diff --git a/tools/BUILD b/tools/BUILD
index ea2b91b02..bfe0d6ef8 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -26,7 +26,7 @@ java_package_configuration(
         "-Xep:ReferenceEquality:WARN",
         "-Xep:StringEquality:WARN",
         "-Xep:WildcardImport:ERROR",
-        "-Xep:AmbiguousMethodReference:WARN",
+        "-Xep:AmbiguousMethodReference:ERROR",
         "-Xep:BadAnnotationImplementation:ERROR",
         "-Xep:BadComparable:WARN",
         "-Xep:BoxedPrimitiveConstructor:ERROR",