diff --git a/boa/src/builtins/array/mod.rs b/boa/src/builtins/array/mod.rs
index 3617fefc82..6654ec61fb 100644
--- a/boa/src/builtins/array/mod.rs
+++ b/boa/src/builtins/array/mod.rs
@@ -15,7 +15,7 @@ mod tests;
 use super::function::{make_builtin_fn, make_constructor_fn};
 use crate::{
     builtins::{
-        object::{ObjectData, INSTANCE_PROTOTYPE, PROTOTYPE},
+        object::{ObjectData, PROTOTYPE},
         property::Property,
         value::{same_value_zero, ResultValue, Value},
     },
@@ -48,8 +48,7 @@ impl Array {
                 .expect("Could not get global object"),
         ));
         array.set_data(ObjectData::Array);
-        array.borrow().set_internal_slot(
-            INSTANCE_PROTOTYPE,
+        array.as_object_mut().expect("array object").set_prototype(
             interpreter
                 .realm()
                 .environment
@@ -116,7 +115,9 @@ impl Array {
         // Set Prototype
         let prototype = ctx.realm.global_obj.get_field("Array").get_field(PROTOTYPE);
 
-        this.set_internal_slot(INSTANCE_PROTOTYPE, prototype);
+        this.as_object_mut()
+            .expect("this should be an array object")
+            .set_prototype(prototype);
         // This value is used by console.log and other routines to match Object type
         // to its Javascript Identifier (global constructor method name)
         this.set_data(ObjectData::Array);
@@ -961,7 +962,7 @@ impl Array {
     ///
     /// The reduce method traverses left to right starting from the first defined value in the array,
     /// accumulating a value using a given callback function. It returns the accumulated value.
-    ///  
+    ///
     /// More information:
     ///  - [ECMAScript reference][spec]
     ///  - [MDN documentation][mdn]
diff --git a/boa/src/builtins/boolean/tests.rs b/boa/src/builtins/boolean/tests.rs
index bc8ffe230d..c0eed466e3 100644
--- a/boa/src/builtins/boolean/tests.rs
+++ b/boa/src/builtins/boolean/tests.rs
@@ -1,7 +1,7 @@
 use crate::{builtins::value::same_value, exec::Interpreter, forward, forward_val, realm::Realm};
 
 /// Test the correct type is returned from call and construct
-#[allow(clippy::result_unwrap_used)]
+#[allow(clippy::unwrap_used)]
 #[test]
 fn construct_and_call() {
     let realm = Realm::create();
@@ -62,7 +62,7 @@ fn instances_have_correct_proto_set() {
     let bool_prototype = forward_val(&mut engine, "boolProto").expect("value expected");
 
     assert!(same_value(
-        &bool_instance.get_internal_slot("__proto__"),
+        &bool_instance.as_object().unwrap().prototype().clone(),
         &bool_prototype
     ));
 }
diff --git a/boa/src/builtins/function/mod.rs b/boa/src/builtins/function/mod.rs
index 83e5de2965..f97e9c480b 100644
--- a/boa/src/builtins/function/mod.rs
+++ b/boa/src/builtins/function/mod.rs
@@ -14,7 +14,7 @@
 use crate::{
     builtins::{
         array::Array,
-        object::{Object, ObjectData, INSTANCE_PROTOTYPE, PROTOTYPE},
+        object::{Object, ObjectData, PROTOTYPE},
         property::Property,
         value::{RcString, ResultValue, Value},
     },
@@ -464,14 +464,10 @@ pub fn make_constructor_fn(
     let mut function = Function::builtin(Vec::new(), body);
     function.flags = FunctionFlags::from_parameters(callable, constructable);
 
-    let mut constructor = Object::function(function);
-
     // Get reference to Function.prototype
     // Create the function object and point its instance prototype to Function.prototype
-    constructor.set_internal_slot(
-        INSTANCE_PROTOTYPE,
-        global.get_field("Function").get_field(PROTOTYPE),
-    );
+    let mut constructor =
+        Object::function(function, global.get_field("Function").get_field(PROTOTYPE));
 
     let length = Property::new()
         .value(Value::from(length))
@@ -527,7 +523,8 @@ where
     let name = name.into();
     let _timer = BoaProfiler::global().start_event(&format!("make_builtin_fn: {}", &name), "init");
 
-    let mut function = Object::function(Function::builtin(Vec::new(), function));
+    // FIXME: function needs the Function prototype set.
+    let mut function = Object::function(Function::builtin(Vec::new(), function), Value::null());
     function.insert_field("length", Value::from(length));
 
     parent
diff --git a/boa/src/builtins/json/tests.rs b/boa/src/builtins/json/tests.rs
index 87033013e6..30f5ce237a 100644
--- a/boa/src/builtins/json/tests.rs
+++ b/boa/src/builtins/json/tests.rs
@@ -1,8 +1,5 @@
 use crate::{
-    builtins::{
-        object::{INSTANCE_PROTOTYPE, PROTOTYPE},
-        value::same_value,
-    },
+    builtins::{object::PROTOTYPE, value::same_value},
     exec::Interpreter,
     forward, forward_val,
     realm::Realm,
@@ -284,10 +281,16 @@ fn json_parse_sets_prototypes() {
     eprintln!("{}", forward(&mut engine, init));
     let object_prototype = forward_val(&mut engine, r#"jsonObj.ob"#)
         .unwrap()
-        .get_internal_slot(INSTANCE_PROTOTYPE);
+        .as_object()
+        .unwrap()
+        .prototype()
+        .clone();
     let array_prototype = forward_val(&mut engine, r#"jsonObj.arr"#)
         .unwrap()
-        .get_internal_slot(INSTANCE_PROTOTYPE);
+        .as_object()
+        .unwrap()
+        .prototype()
+        .clone();
     let global_object_prototype = engine
         .realm
         .global_obj
diff --git a/boa/src/builtins/map/mod.rs b/boa/src/builtins/map/mod.rs
index 3c04dae4c5..75fb8d8654 100644
--- a/boa/src/builtins/map/mod.rs
+++ b/boa/src/builtins/map/mod.rs
@@ -3,7 +3,7 @@
 use super::function::{make_builtin_fn, make_constructor_fn};
 use crate::{
     builtins::{
-        object::{ObjectData, INSTANCE_PROTOTYPE, PROTOTYPE},
+        object::{ObjectData, PROTOTYPE},
         property::Property,
         value::{ResultValue, Value},
     },
@@ -235,7 +235,9 @@ impl Map {
         // Set Prototype
         let prototype = ctx.realm.global_obj.get_field("Map").get_field(PROTOTYPE);
 
-        this.set_internal_slot(INSTANCE_PROTOTYPE, prototype);
+        this.as_object_mut()
+            .expect("this is array object")
+            .set_prototype(prototype);
         // This value is used by console.log and other routines to match Object type
         // to its Javascript Identifier (global constructor method name)
 
diff --git a/boa/src/builtins/object/internal_methods.rs b/boa/src/builtins/object/internal_methods.rs
index 7b79c0c054..bbd51bcf6c 100644
--- a/boa/src/builtins/object/internal_methods.rs
+++ b/boa/src/builtins/object/internal_methods.rs
@@ -6,7 +6,7 @@
 //! [spec]: https://tc39.es/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots
 
 use crate::builtins::{
-    object::{Object, INSTANCE_PROTOTYPE, PROTOTYPE},
+    object::{Object, PROTOTYPE},
     property::Property,
     value::{same_value, RcString, Value},
 };
@@ -363,7 +363,7 @@ impl Object {
     /// [spec]: https://tc39.es/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots-getprototypeof
     #[inline]
     pub fn get_prototype_of(&self) -> Value {
-        self.get_internal_slot(INSTANCE_PROTOTYPE)
+        self.prototype.clone()
     }
 
     /// Helper function to get an immutable internal slot or `Null`.
diff --git a/boa/src/builtins/object/mod.rs b/boa/src/builtins/object/mod.rs
index 4d2b02b1f1..40a5cc98a8 100644
--- a/boa/src/builtins/object/mod.rs
+++ b/boa/src/builtins/object/mod.rs
@@ -44,8 +44,8 @@ mod tests;
 /// Static `prototype`, usually set on constructors as a key to point to their respective prototype object.
 pub static PROTOTYPE: &str = "prototype";
 
-/// Static `__proto__`, usually set on Object instances as a key to point to their respective prototype object.
-pub static INSTANCE_PROTOTYPE: &str = "__proto__";
+// /// Static `__proto__`, usually set on Object instances as a key to point to their respective prototype object.
+// pub static INSTANCE_PROTOTYPE: &str = "__proto__";
 
 /// The internal representation of an JavaScript object.
 #[derive(Debug, Trace, Finalize, Clone)]
@@ -58,6 +58,8 @@ pub struct Object {
     properties: FxHashMap<RcString, Property>,
     /// Symbol Properties
     symbol_properties: FxHashMap<u32, Property>,
+    /// Instance prototype `__proto__`.
+    prototype: Value,
     /// Some rust object that stores internal state
     state: Option<InternalStateCell>,
     /// Whether it can have new properties added to it.
@@ -109,6 +111,7 @@ impl Default for Object {
             internal_slots: FxHashMap::default(),
             properties: FxHashMap::default(),
             symbol_properties: FxHashMap::default(),
+            prototype: Value::null(),
             state: None,
             extensible: true,
         }
@@ -122,7 +125,7 @@ impl Object {
     }
 
     /// Return a new ObjectData struct, with `kind` set to Ordinary
-    pub fn function(function: Function) -> Self {
+    pub fn function(function: Function, prototype: Value) -> Self {
         let _timer = BoaProfiler::global().start_event("Object::Function", "object");
 
         Self {
@@ -130,6 +133,7 @@ impl Object {
             internal_slots: FxHashMap::default(),
             properties: FxHashMap::default(),
             symbol_properties: FxHashMap::default(),
+            prototype,
             state: None,
             extensible: true,
         }
@@ -144,8 +148,7 @@ impl Object {
     // TODO: proto should be a &Value here
     pub fn create(proto: Value) -> Self {
         let mut obj = Self::default();
-        obj.internal_slots
-            .insert(INSTANCE_PROTOTYPE.to_string(), proto);
+        obj.prototype = proto;
         obj
     }
 
@@ -156,6 +159,7 @@ impl Object {
             internal_slots: FxHashMap::default(),
             properties: FxHashMap::default(),
             symbol_properties: FxHashMap::default(),
+            prototype: Value::null(),
             state: None,
             extensible: true,
         }
@@ -168,6 +172,7 @@ impl Object {
             internal_slots: FxHashMap::default(),
             properties: FxHashMap::default(),
             symbol_properties: FxHashMap::default(),
+            prototype: Value::null(),
             state: None,
             extensible: true,
         }
@@ -183,6 +188,7 @@ impl Object {
             internal_slots: FxHashMap::default(),
             properties: FxHashMap::default(),
             symbol_properties: FxHashMap::default(),
+            prototype: Value::null(),
             state: None,
             extensible: true,
         }
@@ -195,6 +201,7 @@ impl Object {
             internal_slots: FxHashMap::default(),
             properties: FxHashMap::default(),
             symbol_properties: FxHashMap::default(),
+            prototype: Value::null(),
             state: None,
             extensible: true,
         }
@@ -419,6 +426,15 @@ impl Object {
     pub fn state_mut(&mut self) -> &mut Option<InternalStateCell> {
         &mut self.state
     }
+
+    pub fn prototype(&self) -> &Value {
+        &self.prototype
+    }
+
+    pub fn set_prototype(&mut self, prototype: Value) {
+        assert!(prototype.is_null() || prototype.is_object());
+        self.prototype = prototype
+    }
 }
 
 /// Create a new object.
@@ -476,14 +492,16 @@ pub fn is(_: &Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
 /// Get the `prototype` of an object.
 pub fn get_prototype_of(_: &Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
     let obj = args.get(0).expect("Cannot get object");
-    Ok(obj.get_field(INSTANCE_PROTOTYPE))
+    Ok(obj
+        .as_object()
+        .map_or_else(Value::undefined, |object| object.prototype.clone()))
 }
 
 /// Set the `prototype` of an object.
 pub fn set_prototype_of(_: &Value, args: &[Value], _: &mut Interpreter) -> ResultValue {
     let obj = args.get(0).expect("Cannot get object").clone();
     let proto = args.get(1).expect("Cannot get object").clone();
-    obj.set_internal_slot(INSTANCE_PROTOTYPE, proto);
+    obj.as_object_mut().unwrap().prototype = proto;
     Ok(obj)
 }
 
diff --git a/boa/src/builtins/string/tests.rs b/boa/src/builtins/string/tests.rs
index ce4673de07..ae11910846 100644
--- a/boa/src/builtins/string/tests.rs
+++ b/boa/src/builtins/string/tests.rs
@@ -86,7 +86,7 @@ fn generic_concat() {
     assert_eq!(a, "100 - 50 = 50");
 }
 
-#[allow(clippy::result_unwrap_used)]
+#[allow(clippy::unwrap_used)]
 #[test]
 /// Test the correct type is returned from call and construct
 fn construct_and_call() {
diff --git a/boa/src/builtins/value/conversions.rs b/boa/src/builtins/value/conversions.rs
index f6c532d3df..dafe62fc74 100644
--- a/boa/src/builtins/value/conversions.rs
+++ b/boa/src/builtins/value/conversions.rs
@@ -174,6 +174,13 @@ impl From<Object> for Value {
     }
 }
 
+impl From<GcObject> for Value {
+    fn from(object: GcObject) -> Self {
+        let _timer = BoaProfiler::global().start_event("From<GcObject>", "value");
+        Value::Object(object)
+    }
+}
+
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
 pub struct TryFromObjectError;
 
diff --git a/boa/src/builtins/value/display.rs b/boa/src/builtins/value/display.rs
index a169884df2..1d936e6d90 100644
--- a/boa/src/builtins/value/display.rs
+++ b/boa/src/builtins/value/display.rs
@@ -21,14 +21,24 @@ macro_rules! print_obj_value {
         }
     };
     (internals of $obj:expr, $display_fn:ident, $indent:expr, $encounters:expr) => {
-        print_obj_value!(impl internal_slots, $obj, |(key, val)| {
-            format!(
-                "{:>width$}: {}",
-                key,
-                $display_fn(&val, $encounters, $indent.wrapping_add(4), true),
-                width = $indent,
-            )
-        })
+        {
+            let object = $obj.borrow();
+            if object.prototype().is_object() {
+                vec![format!(
+                    "{:>width$}: {}",
+                    "__proto__",
+                    $display_fn(object.prototype(), $encounters, $indent.wrapping_add(4), true),
+                    width = $indent,
+                )]
+            } else {
+                vec![format!(
+                    "{:>width$}: {}",
+                    "__proto__",
+                    object.prototype(),
+                    width = $indent,
+                )]
+            }
+        }
     };
     (props of $obj:expr, $display_fn:ident, $indent:expr, $encounters:expr, $print_internals:expr) => {
         print_obj_value!(impl properties, $obj, |(key, val)| {
diff --git a/boa/src/builtins/value/mod.rs b/boa/src/builtins/value/mod.rs
index 8d5447dfe1..2e398ceffa 100644
--- a/boa/src/builtins/value/mod.rs
+++ b/boa/src/builtins/value/mod.rs
@@ -11,10 +11,7 @@ pub use crate::builtins::value::val_type::Type;
 
 use crate::builtins::{
     function::Function,
-    object::{
-        GcObject, InternalState, InternalStateCell, Object, ObjectData, INSTANCE_PROTOTYPE,
-        PROTOTYPE,
-    },
+    object::{GcObject, InternalState, InternalStateCell, Object, ObjectData, PROTOTYPE},
     property::Property,
     BigInt, Symbol,
 };
@@ -176,11 +173,7 @@ impl Value {
     pub fn new_object_from_prototype(proto: Value, data: ObjectData) -> Self {
         let mut object = Object::default();
         object.data = data;
-
-        object
-            .internal_slots_mut()
-            .insert(INSTANCE_PROTOTYPE.to_string(), proto);
-
+        object.set_prototype(proto);
         Self::object(object)
     }
 
@@ -493,10 +486,7 @@ impl Value {
                 let object = object.borrow();
                 match object.properties().get(field) {
                     Some(value) => Some(value.clone()),
-                    None => object
-                        .internal_slots()
-                        .get(INSTANCE_PROTOTYPE)
-                        .and_then(|value| value.get_property(field)),
+                    None => object.prototype().get_property(field),
                 }
             }
             _ => None,
@@ -723,7 +713,8 @@ impl Value {
         // Get Length
         let length = function.params.len();
         // Object with Kind set to function
-        let new_func = Object::function(function);
+        // TODO: FIXME: Add function prototype
+        let new_func = Object::function(function, Value::null());
         // Wrap Object in GC'd Value
         let new_func_val = Value::from(new_func);
         // Set length to parameters
diff --git a/boa/src/exec/mod.rs b/boa/src/exec/mod.rs
index 389a08ab0c..29fba39608 100644
--- a/boa/src/exec/mod.rs
+++ b/boa/src/exec/mod.rs
@@ -26,7 +26,7 @@ use crate::{
     builtins::{
         function::{Function as FunctionObject, FunctionBody, ThisMode},
         number::{f64_to_int32, f64_to_uint32},
-        object::{Object, ObjectData, INSTANCE_PROTOTYPE, PROTOTYPE},
+        object::{Object, ObjectData, PROTOTYPE},
         property::Property,
         value::{RcBigInt, RcString, ResultValue, Type, Value},
         BigInt, Console, Number,
@@ -122,7 +122,7 @@ impl Interpreter {
         P: Into<Box<[FormalParameter]>>,
         B: Into<StatementList>,
     {
-        let function_prototype = &self
+        let function_prototype = self
             .realm
             .environment
             .get_global_object()
@@ -149,10 +149,9 @@ impl Interpreter {
             callable,
         );
 
-        let new_func = Object::function(func);
+        let new_func = Object::function(func, function_prototype);
 
         let val = Value::from(new_func);
-        val.set_internal_slot(INSTANCE_PROTOTYPE, function_prototype.clone());
         val.set_field(PROTOTYPE, proto);
         val.set_field("length", Value::from(params_len));
 
@@ -393,8 +392,7 @@ impl Interpreter {
                                 .expect("Could not get global object"),
                         ));
                         array.set_data(ObjectData::Array);
-                        array.borrow().set_internal_slot(
-                            INSTANCE_PROTOTYPE,
+                        array.as_object_mut().expect("object").set_prototype(
                             self.realm()
                                 .environment
                                 .get_binding_value("Array")
@@ -402,9 +400,9 @@ impl Interpreter {
                                 .borrow()
                                 .get_field(PROTOTYPE),
                         );
-                        array.borrow().set_field("0", key);
-                        array.borrow().set_field("1", value);
-                        array.borrow().set_field("length", Value::from(2));
+                        array.set_field("0", key);
+                        array.set_field("1", value);
+                        array.set_field("length", Value::from(2));
                         array
                     })
                     .collect();
diff --git a/boa/src/exec/new/mod.rs b/boa/src/exec/new/mod.rs
index b611b617aa..472b8817c3 100644
--- a/boa/src/exec/new/mod.rs
+++ b/boa/src/exec/new/mod.rs
@@ -1,7 +1,7 @@
 use super::{Executable, Interpreter};
 use crate::{
     builtins::{
-        object::{ObjectData, INSTANCE_PROTOTYPE, PROTOTYPE},
+        object::{ObjectData, PROTOTYPE},
         value::{ResultValue, Value},
     },
     syntax::ast::node::New,
@@ -23,7 +23,9 @@ impl Executable for New {
         }
         let this = Value::new_object(None);
         // Create a blank object, then set its __proto__ property to the [Constructor].prototype
-        this.set_internal_slot(INSTANCE_PROTOTYPE, func_object.get_field(PROTOTYPE));
+        this.as_object_mut()
+            .expect("this was not an object")
+            .set_prototype(func_object.get_field(PROTOTYPE));
 
         match func_object {
             Value::Object(ref obj) => {
diff --git a/boa/src/exec/tests.rs b/boa/src/exec/tests.rs
index 68cdaa39f6..801eb8555b 100644
--- a/boa/src/exec/tests.rs
+++ b/boa/src/exec/tests.rs
@@ -657,7 +657,7 @@ fn unary_delete() {
 #[cfg(test)]
 mod in_operator {
     use super::*;
-    use crate::{builtins::object::INSTANCE_PROTOTYPE, forward_val};
+    use crate::forward_val;
     #[test]
     fn propery_in_object() {
         let p_in_o = r#"
@@ -762,7 +762,7 @@ mod in_operator {
         "#;
         forward(&mut engine, scenario);
         let a = forward_val(&mut engine, "bar").unwrap();
-        assert!(a.get_internal_slot(INSTANCE_PROTOTYPE).is_object(), true);
+        assert!(a.as_object().unwrap().prototype().is_object());
     }
 }
 
@@ -1122,7 +1122,7 @@ fn check_this_binding_in_object_literal() {
             a: 3,
             bar: function () { return this.a + 5 }
         };
-    
+
         foo.bar()
         "#;
 
diff --git a/boa/src/syntax/parser/tests.rs b/boa/src/syntax/parser/tests.rs
index cf41a996c1..2e238ec401 100644
--- a/boa/src/syntax/parser/tests.rs
+++ b/boa/src/syntax/parser/tests.rs
@@ -14,7 +14,7 @@ use crate::syntax::{
 };
 
 /// Checks that the given JavaScript string gives the expected expression.
-#[allow(clippy::result_unwrap_used)]
+#[allow(clippy::unwrap_used)]
 // TODO: #[track_caller]: https://github.com/rust-lang/rust/issues/47809
 pub(super) fn check_parser<L>(js: &str, expr: L)
 where