diff --git a/boa_parser/src/lexer/identifier.rs b/boa_parser/src/lexer/identifier.rs
index aca96e5aef..732f105f8f 100644
--- a/boa_parser/src/lexer/identifier.rs
+++ b/boa_parser/src/lexer/identifier.rs
@@ -1,6 +1,8 @@
 //! This module implements lexing for identifiers (foo, myvar, etc.) used in ECMAScript.
 
-use crate::lexer::{Cursor, Error, StringLiteral, Token, TokenKind, Tokenizer};
+use crate::lexer::{
+    token::ContainsEscapeSequence, Cursor, Error, StringLiteral, Token, TokenKind, Tokenizer,
+};
 use boa_ast::{Keyword, Position, Span};
 use boa_interner::Interner;
 use boa_profiler::Profiler;
@@ -71,7 +73,10 @@ impl<R> Tokenizer<R> for Identifier {
             Ok(Keyword::False) => TokenKind::BooleanLiteral(false),
             Ok(Keyword::Null) => TokenKind::NullLiteral,
             Ok(keyword) => TokenKind::Keyword((keyword, contains_escaped_chars)),
-            _ => TokenKind::identifier(interner.get_or_intern(identifier_name.as_str())),
+            _ => TokenKind::Identifier((
+                interner.get_or_intern(identifier_name.as_str()),
+                ContainsEscapeSequence(contains_escaped_chars),
+            )),
         };
 
         Ok(Token::new(token_kind, Span::new(start_pos, cursor.pos())))
diff --git a/boa_parser/src/lexer/string.rs b/boa_parser/src/lexer/string.rs
index b3e6643f9c..33c6666538 100644
--- a/boa_parser/src/lexer/string.rs
+++ b/boa_parser/src/lexer/string.rs
@@ -1,6 +1,6 @@
 //! Boa's lexing for ECMAScript string literals.
 
-use crate::lexer::{Cursor, Error, Token, TokenKind, Tokenizer};
+use crate::lexer::{token::EscapeSequence, Cursor, Error, Token, TokenKind, Tokenizer};
 use boa_ast::{Position, Span};
 use boa_interner::Interner;
 use boa_profiler::Profiler;
@@ -88,11 +88,11 @@ impl<R> Tokenizer<R> for StringLiteral {
     {
         let _timer = Profiler::global().start_event("StringLiteral", "Lexing");
 
-        let (lit, span) =
+        let (lit, span, escape_sequence) =
             Self::take_string_characters(cursor, start_pos, self.terminator, cursor.strict_mode())?;
 
         Ok(Token::new(
-            TokenKind::string_literal(interner.get_or_intern(&lit[..])),
+            TokenKind::string_literal(interner.get_or_intern(&lit[..]), escape_sequence),
             span,
         ))
     }
@@ -117,11 +117,13 @@ impl StringLiteral {
         start_pos: Position,
         terminator: StringTerminator,
         is_strict_mode: bool,
-    ) -> Result<(Vec<u16>, Span), Error>
+    ) -> Result<(Vec<u16>, Span, Option<EscapeSequence>), Error>
     where
         R: Read,
     {
         let mut buf = Vec::new();
+        let mut escape_sequence = None;
+
         loop {
             let ch_start_pos = cursor.pos();
             let ch = cursor.next_char()?;
@@ -133,12 +135,15 @@ impl StringLiteral {
                     let _timer =
                         Profiler::global().start_event("StringLiteral - escape sequence", "Lexing");
 
-                    if let Some(escape_value) = Self::take_escape_sequence_or_line_continuation(
-                        cursor,
-                        ch_start_pos,
-                        is_strict_mode,
-                        false,
-                    )? {
+                    if let Some((escape_value, escape)) =
+                        Self::take_escape_sequence_or_line_continuation(
+                            cursor,
+                            ch_start_pos,
+                            is_strict_mode,
+                            false,
+                        )?
+                    {
+                        escape_sequence = escape_sequence.or(escape);
                         buf.push_code_point(escape_value);
                     }
                 }
@@ -156,7 +161,7 @@ impl StringLiteral {
             }
         }
 
-        Ok((buf, Span::new(start_pos, cursor.pos())))
+        Ok((buf, Span::new(start_pos, cursor.pos()), escape_sequence))
     }
 
     pub(super) fn take_escape_sequence_or_line_continuation<R>(
@@ -164,7 +169,7 @@ impl StringLiteral {
         start_pos: Position,
         is_strict_mode: bool,
         is_template_literal: bool,
-    ) -> Result<Option<u32>, Error>
+    ) -> Result<Option<(u32, Option<EscapeSequence>)>, Error>
     where
         R: Read,
     {
@@ -176,25 +181,25 @@ impl StringLiteral {
         })?;
 
         let escape_value = match escape_ch {
-            0x0062 /* b */ => Some(0x0008 /* <BS> */),
-            0x0074 /* t */ => Some(0x0009 /* <HT> */),
-            0x006E /* n */ => Some(0x000A /* <LF> */),
-            0x0076 /* v */ => Some(0x000B /* <VT> */),
-            0x0066 /* f */ => Some(0x000C /* <FF> */),
-            0x0072 /* r */ => Some(0x000D /* <CR> */),
-            0x0022 /* " */ => Some(0x0022 /* " */),
-            0x0027 /* ' */ => Some(0x0027 /* ' */),
-            0x005C /* \ */ => Some(0x005C /* \ */),
+            0x0062 /* b */ => Some((0x0008 /* <BS> */, None)),
+            0x0074 /* t */ => Some((0x0009 /* <HT> */, None)),
+            0x006E /* n */ => Some((0x000A /* <LF> */, None)),
+            0x0076 /* v */ => Some((0x000B /* <VT> */, None)),
+            0x0066 /* f */ => Some((0x000C /* <FF> */, None)),
+            0x0072 /* r */ => Some((0x000D /* <CR> */, None)),
+            0x0022 /* " */ => Some((0x0022 /* " */, None)),
+            0x0027 /* ' */ => Some((0x0027 /* ' */, None)),
+            0x005C /* \ */ => Some((0x005C /* \ */, None)),
             0x0030 /* 0 */ if cursor
                 .peek()?
                 .filter(|next_byte| (b'0'..=b'9').contains(next_byte))
                 .is_none() =>
-                Some(0x0000 /* NULL */),
+                Some((0x0000 /* NULL */, None)),
             0x0078 /* x */ => {
-                Some(Self::take_hex_escape_sequence(cursor, start_pos)?)
+                Some((Self::take_hex_escape_sequence(cursor, start_pos)?, None))
             }
             0x0075 /* u */ => {
-                Some(Self::take_unicode_escape_sequence(cursor, start_pos)?)
+                Some((Self::take_unicode_escape_sequence(cursor, start_pos)?, None))
             }
             0x0038 /* 8 */ | 0x0039 /* 9 */ => {
                 // Grammar: NonOctalDecimalEscapeSequence
@@ -209,7 +214,7 @@ impl StringLiteral {
                         start_pos,
                     ));
                 }
-                    Some(escape_ch)
+                    Some((escape_ch, Some(EscapeSequence::NonOctalDecimal)))
             }
             _ if (0x0030..=0x0037 /* '0'..='7' */).contains(&escape_ch) => {
                 if is_template_literal {
@@ -226,10 +231,10 @@ impl StringLiteral {
                     ));
                 }
 
-                Some(Self::take_legacy_octal_escape_sequence(
+                Some((Self::take_legacy_octal_escape_sequence(
                     cursor,
                     escape_ch.try_into().expect("an ascii char must not fail to convert"),
-                )?)
+                )?, Some(EscapeSequence::LegacyOctal)))
             }
             _ if Self::is_line_terminator(escape_ch) => {
                 // Grammar: LineContinuation
@@ -238,7 +243,7 @@ impl StringLiteral {
                 None
             }
             _ => {
-                Some(escape_ch)
+                Some((escape_ch, None))
             }
         };
 
diff --git a/boa_parser/src/lexer/template.rs b/boa_parser/src/lexer/template.rs
index 7a666d745e..23e92854be 100644
--- a/boa_parser/src/lexer/template.rs
+++ b/boa_parser/src/lexer/template.rs
@@ -60,7 +60,7 @@ impl TemplateString {
                         true,
                     )?;
 
-                    if let Some(escape_value) = escape_value {
+                    if let Some((escape_value, _)) = escape_value {
                         buf.push_code_point(escape_value);
                     }
                 }
diff --git a/boa_parser/src/lexer/tests.rs b/boa_parser/src/lexer/tests.rs
index 01616e1f4d..40f984df44 100644
--- a/boa_parser/src/lexer/tests.rs
+++ b/boa_parser/src/lexer/tests.rs
@@ -2,8 +2,9 @@
 #![allow(clippy::indexing_slicing)]
 
 use crate::lexer::{
-    template::TemplateString, token::Numeric, Cursor, Error, Interner, Lexer, Position, Punctuator,
-    Read, Span, TokenKind,
+    template::TemplateString,
+    token::{ContainsEscapeSequence, EscapeSequence, Numeric},
+    Cursor, Error, Interner, Lexer, Position, Punctuator, Read, Span, TokenKind,
 };
 use boa_ast::Keyword;
 use boa_interner::Sym;
@@ -94,9 +95,18 @@ fn check_identifier() {
         TokenKind::identifier(
             interner.get_or_intern_static("x\u{200C}\u{200D}", utf16!("x\u{200C}\u{200D}")),
         ),
-        TokenKind::identifier(interner.get_or_intern_static("x", utf16!("x"))),
-        TokenKind::identifier(interner.get_or_intern_static("xx", utf16!("xx"))),
-        TokenKind::identifier(interner.get_or_intern_static("xxx", utf16!("xxx"))),
+        TokenKind::Identifier((
+            interner.get_or_intern_static("x", utf16!("x")),
+            ContainsEscapeSequence(true),
+        )),
+        TokenKind::Identifier((
+            interner.get_or_intern_static("xx", utf16!("xx")),
+            ContainsEscapeSequence(true),
+        )),
+        TokenKind::Identifier((
+            interner.get_or_intern_static("xxx", utf16!("xxx")),
+            ContainsEscapeSequence(true),
+        )),
     ];
 
     expect_tokens(&mut lexer, &expected, interner);
@@ -141,8 +151,8 @@ fn check_string() {
     let a_sym = interner.get_or_intern_static("aaa", utf16!("aaa"));
     let b_sym = interner.get_or_intern_static("bbb", utf16!("bbb"));
     let expected = [
-        TokenKind::string_literal(a_sym),
-        TokenKind::string_literal(b_sym),
+        TokenKind::string_literal(a_sym, None),
+        TokenKind::string_literal(b_sym, None),
     ];
 
     expect_tokens(&mut lexer, &expected, interner);
@@ -305,7 +315,7 @@ fn check_variable_definition_tokens() {
         TokenKind::Keyword((Keyword::Let, false)),
         TokenKind::identifier(a_sym),
         TokenKind::Punctuator(Punctuator::Assign),
-        TokenKind::string_literal(hello_sym),
+        TokenKind::string_literal(hello_sym, None),
         TokenKind::Punctuator(Punctuator::Semicolon),
     ];
 
@@ -943,7 +953,7 @@ fn string_unicode() {
 
     let sym = interner.get_or_intern_static("中文", utf16!("中文"));
     let expected = [
-        TokenKind::StringLiteral(sym),
+        TokenKind::StringLiteral((sym, None)),
         TokenKind::Punctuator(Punctuator::Semicolon),
     ];
 
@@ -957,7 +967,7 @@ fn string_unicode_escape_with_braces() {
 
     let sym =
         interner.get_or_intern_static("{\u{20ac}\u{a0}\u{a0}}", utf16!("{\u{20ac}\u{a0}\u{a0}}"));
-    let expected = [TokenKind::StringLiteral(sym)];
+    let expected = [TokenKind::StringLiteral((sym, None))];
 
     expect_tokens(&mut lexer, &expected, interner);
 
@@ -992,7 +1002,7 @@ fn string_unicode_escape_with_braces_2() {
     let interner = &mut Interner::default();
 
     let sym = interner.get_or_intern_static("\u{20ac}\u{a0}\u{a0}", utf16!("\u{20ac}\u{a0}\u{a0}"));
-    let expected = [TokenKind::StringLiteral(sym)];
+    let expected = [TokenKind::StringLiteral((sym, None))];
 
     expect_tokens(&mut lexer, &expected, interner);
 }
@@ -1005,7 +1015,7 @@ fn string_with_single_escape() {
     let interner = &mut Interner::default();
 
     let sym = interner.get_or_intern_static("Б", utf16!("Б"));
-    let expected = [TokenKind::StringLiteral(sym)];
+    let expected = [TokenKind::StringLiteral((sym, None))];
 
     expect_tokens(&mut lexer, &expected, interner);
 }
@@ -1027,7 +1037,10 @@ fn string_legacy_octal_escape() {
         let interner = &mut Interner::default();
 
         let sym = interner.get_or_intern(expected.encode_utf16().collect::<Vec<_>>().as_slice());
-        let expected_tokens = [TokenKind::StringLiteral(sym)];
+        let expected_tokens = [TokenKind::StringLiteral((
+            sym,
+            Some(EscapeSequence::LegacyOctal),
+        ))];
 
         expect_tokens(&mut lexer, &expected_tokens, interner);
     }
@@ -1057,7 +1070,7 @@ fn string_zero_escape() {
         let interner = &mut Interner::default();
 
         let sym = interner.get_or_intern(expected.encode_utf16().collect::<Vec<_>>().as_slice());
-        let expected_tokens = [TokenKind::StringLiteral(sym)];
+        let expected_tokens = [TokenKind::StringLiteral((sym, None))];
 
         expect_tokens(&mut lexer, &expected_tokens, interner);
     }
@@ -1072,7 +1085,10 @@ fn string_non_octal_decimal_escape() {
         let interner = &mut Interner::default();
 
         let sym = interner.get_or_intern(expected.encode_utf16().collect::<Vec<_>>().as_slice());
-        let expected_tokens = [TokenKind::StringLiteral(sym)];
+        let expected_tokens = [TokenKind::StringLiteral((
+            sym,
+            Some(EscapeSequence::NonOctalDecimal),
+        ))];
 
         expect_tokens(&mut lexer, &expected_tokens, interner);
     }
@@ -1101,7 +1117,7 @@ fn string_line_continuation() {
     let interner = &mut Interner::default();
 
     let sym = interner.get_or_intern_static("hello world", utf16!("hello world"));
-    let expected_tokens = [TokenKind::StringLiteral(sym)];
+    let expected_tokens = [TokenKind::StringLiteral((sym, None))];
 
     expect_tokens(&mut lexer, &expected_tokens, interner);
 }
diff --git a/boa_parser/src/lexer/token.rs b/boa_parser/src/lexer/token.rs
index 5fcd06cb1d..f7bf2ba06a 100644
--- a/boa_parser/src/lexer/token.rs
+++ b/boa_parser/src/lexer/token.rs
@@ -99,7 +99,7 @@ pub enum TokenKind {
     EOF,
 
     /// An identifier.
-    Identifier(Sym),
+    Identifier((Sym, ContainsEscapeSequence)),
 
     /// A private identifier.
     PrivateIdentifier(Sym),
@@ -117,7 +117,7 @@ pub enum TokenKind {
     Punctuator(Punctuator),
 
     /// A string literal.
-    StringLiteral(Sym),
+    StringLiteral((Sym, Option<EscapeSequence>)),
 
     /// A part of a template literal without substitution.
     TemplateNoSubstitution(TemplateString),
@@ -175,7 +175,7 @@ impl TokenKind {
     /// Creates an `Identifier` token type.
     #[must_use]
     pub const fn identifier(ident: Sym) -> Self {
-        Self::Identifier(ident)
+        Self::Identifier((ident, ContainsEscapeSequence(false)))
     }
 
     /// Creates a `NumericLiteral` token kind.
@@ -194,8 +194,8 @@ impl TokenKind {
 
     /// Creates a `StringLiteral` token type.
     #[must_use]
-    pub const fn string_literal(lit: Sym) -> Self {
-        Self::StringLiteral(lit)
+    pub const fn string_literal(lit: Sym, escape_sequence: Option<EscapeSequence>) -> Self {
+        Self::StringLiteral((lit, escape_sequence))
     }
 
     /// Creates a `TemplateMiddle` token type.
@@ -234,7 +234,7 @@ impl TokenKind {
         match *self {
             Self::BooleanLiteral(val) => val.to_string(),
             Self::EOF => "end of file".to_owned(),
-            Self::Identifier(ident) => interner.resolve_expect(ident).to_string(),
+            Self::Identifier((ident, _)) => interner.resolve_expect(ident).to_string(),
             Self::PrivateIdentifier(ident) => format!("#{}", interner.resolve_expect(ident)),
             Self::Keyword((word, _)) => word.to_string(),
             Self::NullLiteral => "null".to_owned(),
@@ -242,7 +242,7 @@ impl TokenKind {
             Self::NumericLiteral(Numeric::Integer(num)) => num.to_string(),
             Self::NumericLiteral(Numeric::BigInt(ref num)) => format!("{num}n"),
             Self::Punctuator(punc) => punc.to_string(),
-            Self::StringLiteral(lit) => interner.resolve_expect(lit).to_string(),
+            Self::StringLiteral((lit, _)) => interner.resolve_expect(lit).to_string(),
             Self::TemplateNoSubstitution(ts) | Self::TemplateMiddle(ts) => {
                 interner.resolve_expect(ts.as_raw()).to_string()
             }
@@ -258,3 +258,29 @@ impl TokenKind {
         }
     }
 }
+
+/// Indicates the type of an escape sequence.
+#[cfg_attr(feature = "deser", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EscapeSequence {
+    /// A legacy escape sequence starting with `0` - `7`.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#prod-LegacyOctalEscapeSequence
+    LegacyOctal,
+
+    /// A octal escape sequence starting with `8` - `9`.
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#prod-NonOctalDecimalEscapeSequence
+    NonOctalDecimal,
+}
+
+/// Indicates if an identifier contains an escape sequence.
+#[cfg_attr(feature = "deser", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ContainsEscapeSequence(pub bool);
diff --git a/boa_parser/src/parser/expression/identifiers.rs b/boa_parser/src/parser/expression/identifiers.rs
index e82da53d18..ac325d38fd 100644
--- a/boa_parser/src/parser/expression/identifiers.rs
+++ b/boa_parser/src/parser/expression/identifiers.rs
@@ -65,7 +65,7 @@ where
         let token = cursor.next(interner).or_abrupt()?;
 
         match token.kind() {
-            TokenKind::Identifier(ident)
+            TokenKind::Identifier((ident, _))
                 if cursor.strict_mode() && RESERVED_IDENTIFIERS_STRICT.contains(ident) =>
             {
                 Err(Error::general(
@@ -73,7 +73,7 @@ where
                     token.span().start(),
                 ))
             }
-            TokenKind::Identifier(ident) => Ok(Identifier::new(*ident)),
+            TokenKind::Identifier((ident, _)) => Ok(Identifier::new(*ident)),
             TokenKind::Keyword((Keyword::Let, _)) if cursor.strict_mode() => Err(Error::general(
                 "using future reserved keyword not allowed in strict mode IdentifierReference",
                 token.span().start(),
@@ -155,19 +155,19 @@ where
         let next_token = cursor.next(interner).or_abrupt()?;
 
         match next_token.kind() {
-            TokenKind::Identifier(Sym::ARGUMENTS) if cursor.strict_mode() => {
+            TokenKind::Identifier((Sym::ARGUMENTS, _)) if cursor.strict_mode() => {
                 Err(Error::lex(LexError::Syntax(
                     "unexpected identifier 'arguments' in strict mode".into(),
                     next_token.span().start(),
                 )))
             }
-            TokenKind::Identifier(Sym::EVAL) if cursor.strict_mode() => {
+            TokenKind::Identifier((Sym::EVAL, _)) if cursor.strict_mode() => {
                 Err(Error::lex(LexError::Syntax(
                     "unexpected identifier 'eval' in strict mode".into(),
                     next_token.span().start(),
                 )))
             }
-            TokenKind::Identifier(ident) => {
+            TokenKind::Identifier((ident, _)) => {
                 if cursor.strict_mode() && RESERVED_IDENTIFIERS_STRICT.contains(ident) {
                     return Err(Error::general(
                         "using future reserved keyword not allowed in strict mode",
diff --git a/boa_parser/src/parser/expression/left_hand_side/call.rs b/boa_parser/src/parser/expression/left_hand_side/call.rs
index 14ec399af1..ecd35bc338 100644
--- a/boa_parser/src/parser/expression/left_hand_side/call.rs
+++ b/boa_parser/src/parser/expression/left_hand_side/call.rs
@@ -98,7 +98,9 @@ where
                     cursor.advance(interner);
 
                     let access = match cursor.next(interner).or_abrupt()?.kind() {
-                        TokenKind::Identifier(name) => SimplePropertyAccess::new(lhs, *name).into(),
+                        TokenKind::Identifier((name, _)) => {
+                            SimplePropertyAccess::new(lhs, *name).into()
+                        }
                         TokenKind::Keyword((kw, _)) => {
                             SimplePropertyAccess::new(lhs, kw.to_sym(interner)).into()
                         }
diff --git a/boa_parser/src/parser/expression/left_hand_side/member.rs b/boa_parser/src/parser/expression/left_hand_side/member.rs
index 4df236e656..71b3b209ed 100644
--- a/boa_parser/src/parser/expression/left_hand_side/member.rs
+++ b/boa_parser/src/parser/expression/left_hand_side/member.rs
@@ -7,7 +7,7 @@
 
 use super::arguments::Arguments;
 use crate::{
-    lexer::{InputElement, TokenKind},
+    lexer::{token::ContainsEscapeSequence, InputElement, TokenKind},
     parser::{
         expression::{
             left_hand_side::template::TaggedTemplateLiteral, primary::PrimaryExpression, Expression,
@@ -85,7 +85,13 @@ where
                 if cursor.next_if(Punctuator::Dot, interner)?.is_some() {
                     let token = cursor.next(interner).or_abrupt()?;
                     match token.kind() {
-                        TokenKind::Identifier(Sym::TARGET) => {
+                        TokenKind::Identifier((Sym::TARGET, ContainsEscapeSequence(true))) => {
+                            return Err(Error::general(
+                                "'new.target' must not contain escaped characters",
+                                token.span().start(),
+                            ));
+                        }
+                        TokenKind::Identifier((Sym::TARGET, ContainsEscapeSequence(false))) => {
                             return Ok(ast::Expression::NewTarget)
                         }
                         _ => {
@@ -116,7 +122,7 @@ where
                     TokenKind::Punctuator(Punctuator::Dot) => {
                         let token = cursor.next(interner).or_abrupt()?;
                         let field = match token.kind() {
-                            TokenKind::Identifier(name) => {
+                            TokenKind::Identifier((name, _)) => {
                                 SuperPropertyAccess::new(PropertyAccessField::from(*name))
                             }
                             TokenKind::Keyword((kw, _)) => {
@@ -178,7 +184,9 @@ where
                     let token = cursor.next(interner).or_abrupt()?;
 
                     let access = match token.kind() {
-                        TokenKind::Identifier(name) => SimplePropertyAccess::new(lhs, *name).into(),
+                        TokenKind::Identifier((name, _)) => {
+                            SimplePropertyAccess::new(lhs, *name).into()
+                        }
                         TokenKind::Keyword((kw, _)) => {
                             SimplePropertyAccess::new(lhs, kw.to_sym(interner)).into()
                         }
diff --git a/boa_parser/src/parser/expression/left_hand_side/optional/mod.rs b/boa_parser/src/parser/expression/left_hand_side/optional/mod.rs
index f8dbd51cbb..f44bffb2e3 100644
--- a/boa_parser/src/parser/expression/left_hand_side/optional/mod.rs
+++ b/boa_parser/src/parser/expression/left_hand_side/optional/mod.rs
@@ -66,7 +66,7 @@ where
             interner: &mut Interner,
         ) -> ParseResult<OptionalOperationKind> {
             let item = match token.kind() {
-                TokenKind::Identifier(name) => OptionalOperationKind::SimplePropertyAccess {
+                TokenKind::Identifier((name, _)) => OptionalOperationKind::SimplePropertyAccess {
                     field: PropertyAccessField::Const(*name),
                 },
                 TokenKind::Keyword((kw, _)) => OptionalOperationKind::SimplePropertyAccess {
diff --git a/boa_parser/src/parser/expression/primary/mod.rs b/boa_parser/src/parser/expression/primary/mod.rs
index 37e5e7da0b..f34bacabc2 100644
--- a/boa_parser/src/parser/expression/primary/mod.rs
+++ b/boa_parser/src/parser/expression/primary/mod.rs
@@ -209,7 +209,7 @@ where
             )) => IdentifierReference::new(self.allow_yield, self.allow_await)
                 .parse(cursor, interner)
                 .map(Into::into),
-            TokenKind::StringLiteral(lit) => {
+            TokenKind::StringLiteral((lit, _)) => {
                 let node = Literal::from(*lit).into();
                 cursor.advance(interner);
                 Ok(node)
diff --git a/boa_parser/src/parser/expression/primary/object_initializer/mod.rs b/boa_parser/src/parser/expression/primary/object_initializer/mod.rs
index 31b8219b15..2d497785a7 100644
--- a/boa_parser/src/parser/expression/primary/object_initializer/mod.rs
+++ b/boa_parser/src/parser/expression/primary/object_initializer/mod.rs
@@ -11,7 +11,10 @@
 mod tests;
 
 use crate::{
-    lexer::{token::Numeric, Error as LexError, TokenKind},
+    lexer::{
+        token::{ContainsEscapeSequence, Numeric},
+        Error as LexError, TokenKind,
+    },
     parser::{
         expression::{identifiers::IdentifierReference, AssignmentExpression},
         function::{FormalParameter, FormalParameters, FunctionBody, UniqueFormalParameters},
@@ -198,6 +201,7 @@ where
             cursor.peek(1, interner).or_abrupt()?.kind(),
             TokenKind::Punctuator(Punctuator::OpenParen | Punctuator::Colon)
         );
+
         let token = cursor.peek(0, interner).or_abrupt()?;
         match token.kind() {
             TokenKind::Keyword((Keyword::Async, true)) if is_keyword => {
@@ -258,7 +262,9 @@ where
             _ => {}
         }
 
-        if cursor.peek(0, interner).or_abrupt()?.kind() == &TokenKind::Punctuator(Punctuator::Mul) {
+        let token = cursor.peek(0, interner).or_abrupt()?;
+
+        if token.kind() == &TokenKind::Punctuator(Punctuator::Mul) {
             let position = cursor.peek(0, interner).or_abrupt()?.span().start();
             let (class_element_name, method) =
                 GeneratorMethod::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
@@ -284,6 +290,13 @@ where
             }
         }
 
+        let set_or_get_escaped_position = match token.kind() {
+            TokenKind::Identifier((Sym::GET | Sym::SET, ContainsEscapeSequence(true))) => {
+                Some(token.span().start())
+            }
+            _ => None,
+        };
+
         let mut property_name =
             PropertyName::new(self.allow_yield, self.allow_await).parse(cursor, interner)?;
 
@@ -306,6 +319,13 @@ where
         match property_name {
             // MethodDefinition[?Yield, ?Await] -> get ClassElementName[?Yield, ?Await] ( ) { FunctionBody[~Yield, ~Await] }
             property::PropertyName::Literal(str) if str == Sym::GET && !ordinary_method => {
+                if let Some(position) = set_or_get_escaped_position {
+                    return Err(Error::general(
+                        "Keyword must not contain escaped characters",
+                        position,
+                    ));
+                }
+
                 let position = cursor.peek(0, interner).or_abrupt()?.span().start();
 
                 property_name = PropertyName::new(self.allow_yield, self.allow_await)
@@ -359,6 +379,13 @@ where
             }
             // MethodDefinition[?Yield, ?Await] -> set ClassElementName[?Yield, ?Await] ( PropertySetParameterList ) { FunctionBody[~Yield, ~Await] }
             property::PropertyName::Literal(str) if str == Sym::SET && !ordinary_method => {
+                if let Some(position) = set_or_get_escaped_position {
+                    return Err(Error::general(
+                        "Keyword must not contain escaped characters",
+                        position,
+                    ));
+                }
+
                 property_name = PropertyName::new(self.allow_yield, self.allow_await)
                     .parse(cursor, interner)?;
 
@@ -551,7 +578,9 @@ where
                 cursor.expect(Punctuator::CloseBracket, "expected token ']'", interner)?;
                 return Ok(node.into());
             }
-            TokenKind::Identifier(name) | TokenKind::StringLiteral(name) => (*name).into(),
+            TokenKind::Identifier((name, _)) | TokenKind::StringLiteral((name, _)) => {
+                (*name).into()
+            }
             TokenKind::NumericLiteral(num) => match num {
                 Numeric::Rational(num) => Expression::Literal(Literal::from(*num)).into(),
                 Numeric::Integer(num) => Expression::Literal(Literal::from(*num)).into(),
diff --git a/boa_parser/src/parser/statement/declaration/hoistable/class_decl/mod.rs b/boa_parser/src/parser/statement/declaration/hoistable/class_decl/mod.rs
index cc03fc50ea..591c4c534e 100644
--- a/boa_parser/src/parser/statement/declaration/hoistable/class_decl/mod.rs
+++ b/boa_parser/src/parser/statement/declaration/hoistable/class_decl/mod.rs
@@ -2,7 +2,7 @@
 mod tests;
 
 use crate::{
-    lexer::{Error as LexError, TokenKind},
+    lexer::{token::ContainsEscapeSequence, Error as LexError, TokenKind},
     parser::{
         expression::{
             AssignmentExpression, AsyncGeneratorMethod, AsyncMethod, BindingIdentifier,
@@ -595,7 +595,8 @@ where
                 cursor.advance(interner);
                 return Ok((None, None));
             }
-            TokenKind::Identifier(Sym::STATIC) => {
+            TokenKind::Identifier((Sym::STATIC, ContainsEscapeSequence(contains_escape))) => {
+                let contains_escape = *contains_escape;
                 let token = cursor.peek(1, interner).or_abrupt()?;
                 match token.kind() {
                     TokenKind::Identifier(_)
@@ -607,6 +608,12 @@ where
                     | TokenKind::Punctuator(
                         Punctuator::OpenBracket | Punctuator::Mul | Punctuator::OpenBlock,
                     ) => {
+                        if contains_escape {
+                            return Err(Error::general(
+                                "keyword must not contain escaped characters",
+                                token.span().start(),
+                            ));
+                        }
                         // this "static" is a keyword.
                         cursor.advance(interner);
                         true
@@ -630,7 +637,7 @@ where
         let token = cursor.peek(0, interner).or_abrupt()?;
         let position = token.span().start();
         let element = match token.kind() {
-            TokenKind::Identifier(Sym::CONSTRUCTOR) if !r#static => {
+            TokenKind::Identifier((Sym::CONSTRUCTOR, _)) if !r#static => {
                 cursor.advance(interner);
                 let strict = cursor.strict_mode();
                 cursor.set_strict_mode(true);
@@ -708,11 +715,13 @@ where
             TokenKind::Punctuator(Punctuator::Mul) => {
                 let token = cursor.peek(1, interner).or_abrupt()?;
                 let name_position = token.span().start();
-                if token.kind() == &TokenKind::Identifier(Sym::CONSTRUCTOR) && !r#static {
-                    return Err(Error::general(
-                        "class constructor may not be a generator method",
-                        token.span().start(),
-                    ));
+                if !r#static {
+                    if let TokenKind::Identifier((Sym::CONSTRUCTOR, _)) = token.kind() {
+                        return Err(Error::general(
+                            "class constructor may not be a generator method",
+                            token.span().start(),
+                        ));
+                    }
                 }
                 let strict = cursor.strict_mode();
                 cursor.set_strict_mode(true);
@@ -764,13 +773,20 @@ where
                     TokenKind::Punctuator(Punctuator::Mul) => {
                         let token = cursor.peek(1, interner).or_abrupt()?;
                         let name_position = token.span().start();
-                        if token.kind() == &TokenKind::PrivateIdentifier(Sym::CONSTRUCTOR)
-                            || token.kind() == &TokenKind::Identifier(Sym::CONSTRUCTOR) && !r#static
-                        {
-                            return Err(Error::general(
-                                "class constructor may not be a generator method",
-                                token.span().start(),
-                            ));
+                        match token.kind() {
+                            TokenKind::PrivateIdentifier(Sym::CONSTRUCTOR) => {
+                                return Err(Error::general(
+                                    "class constructor may not be a private method",
+                                    token.span().start(),
+                                ));
+                            }
+                            TokenKind::Identifier((Sym::CONSTRUCTOR, _)) if !r#static => {
+                                return Err(Error::general(
+                                    "class constructor may not be a generator method",
+                                    token.span().start(),
+                                ));
+                            }
+                            _ => {}
                         }
                         let strict = cursor.strict_mode();
                         cursor.set_strict_mode(true);
@@ -808,7 +824,7 @@ where
                             }
                         }
                     }
-                    TokenKind::Identifier(Sym::CONSTRUCTOR) if !r#static => {
+                    TokenKind::Identifier((Sym::CONSTRUCTOR, _)) if !r#static => {
                         return Err(Error::general(
                             "class constructor may not be an async method",
                             token.span().start(),
@@ -859,7 +875,13 @@ where
                     }
                 }
             }
-            TokenKind::Identifier(Sym::GET) if is_keyword => {
+            TokenKind::Identifier((Sym::GET, ContainsEscapeSequence(true))) if is_keyword => {
+                return Err(Error::general(
+                    "keyword must not contain escaped characters",
+                    token.span().start(),
+                ))
+            }
+            TokenKind::Identifier((Sym::GET, ContainsEscapeSequence(false))) if is_keyword => {
                 cursor.advance(interner);
                 let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
@@ -911,7 +933,7 @@ where
                             )
                         }
                     }
-                    TokenKind::Identifier(Sym::CONSTRUCTOR) if !r#static => {
+                    TokenKind::Identifier((Sym::CONSTRUCTOR, _)) if !r#static => {
                         return Err(Error::general(
                             "class constructor may not be a getter method",
                             token.span().start(),
@@ -984,7 +1006,13 @@ where
                     }
                 }
             }
-            TokenKind::Identifier(Sym::SET) if is_keyword => {
+            TokenKind::Identifier((Sym::SET, ContainsEscapeSequence(true))) if is_keyword => {
+                return Err(Error::general(
+                    "keyword must not contain escaped characters",
+                    token.span().start(),
+                ))
+            }
+            TokenKind::Identifier((Sym::SET, ContainsEscapeSequence(false))) if is_keyword => {
                 cursor.advance(interner);
                 let token = cursor.peek(0, interner).or_abrupt()?;
                 match token.kind() {
@@ -1036,7 +1064,7 @@ where
                             )
                         }
                     }
-                    TokenKind::Identifier(Sym::CONSTRUCTOR) if !r#static => {
+                    TokenKind::Identifier((Sym::CONSTRUCTOR, _)) if !r#static => {
                         return Err(Error::general(
                             "class constructor may not be a setter method",
                             token.span().start(),
diff --git a/boa_parser/src/parser/statement/mod.rs b/boa_parser/src/parser/statement/mod.rs
index 3d47d4cda2..79fc5ac8a2 100644
--- a/boa_parser/src/parser/statement/mod.rs
+++ b/boa_parser/src/parser/statement/mod.rs
@@ -37,7 +37,7 @@ use self::{
     variable::VariableStatement,
 };
 use crate::{
-    lexer::{Error as LexError, InputElement, Token, TokenKind},
+    lexer::{token::EscapeSequence, Error as LexError, InputElement, Token, TokenKind},
     parser::{
         expression::{BindingIdentifier, Initializer, PropertyName},
         AllowAwait, AllowReturn, AllowYield, Cursor, OrAbrupt, ParseResult, TokenParser,
@@ -282,10 +282,17 @@ where
         let global_strict = cursor.strict_mode();
         let mut directive_prologues = self.directive_prologues;
         let mut strict = self.strict;
+        let mut string_literal_escape_sequence = None;
 
         loop {
             match cursor.peek(0, interner)? {
                 Some(token) if self.break_nodes.contains(token.kind()) => break,
+                Some(token) if directive_prologues && string_literal_escape_sequence.is_none() => {
+                    if let TokenKind::StringLiteral((_, Some(escape_sequence))) = token.kind() {
+                        string_literal_escape_sequence =
+                            Some((token.span().start(), *escape_sequence));
+                    }
+                }
                 None => break,
                 _ => {}
             }
@@ -306,6 +313,21 @@ where
                     ) {
                         cursor.set_strict_mode(true);
                         strict = true;
+
+                        if let Some((position, escape_sequence)) = string_literal_escape_sequence {
+                            match escape_sequence {
+                                EscapeSequence::LegacyOctal => return Err(Error::general(
+                                    "legacy octal escape sequences are not allowed in strict mode",
+                                    position,
+                                )),
+                                EscapeSequence::NonOctalDecimal => {
+                                    return Err(Error::general(
+                                        "decimal escape sequences are not allowed in strict mode",
+                                        position,
+                                    ))
+                                }
+                            }
+                        }
                     }
                 } else {
                     directive_prologues = false;