diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index da762131c5..0f57e5f7a0 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1733,6 +1733,10 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
     native_context()->set_array_for_each_iterator(*for_each_fun);
     SimpleInstallFunction(isolate_, proto, "filter", Builtins::kArrayFilter, 1,
                           false);
+    SimpleInstallFunction(isolate_, proto, "flat",
+                          Builtins::kArrayPrototypeFlat, 0, false);
+    SimpleInstallFunction(isolate_, proto, "flatMap",
+                          Builtins::kArrayPrototypeFlatMap, 1, false);
     SimpleInstallFunction(isolate_, proto, "map", Builtins::kArrayMap, 1,
                           false);
     SimpleInstallFunction(isolate_, proto, "every", Builtins::kArrayEvery, 1,
@@ -4214,18 +4218,6 @@ void Genesis::InitializeGlobal_harmony_sharedarraybuffer() {
   InstallToStringTag(isolate_, isolate()->atomics_object(), "Atomics");
 }
 
-void Genesis::InitializeGlobal_harmony_array_flat() {
-  if (!FLAG_harmony_array_flat) return;
-  Handle<JSFunction> array_constructor(native_context()->array_function(),
-                                       isolate());
-  Handle<JSObject> array_prototype(
-      JSObject::cast(array_constructor->instance_prototype()), isolate());
-  SimpleInstallFunction(isolate(), array_prototype, "flat",
-                        Builtins::kArrayPrototypeFlat, 0, false);
-  SimpleInstallFunction(isolate(), array_prototype, "flatMap",
-                        Builtins::kArrayPrototypeFlatMap, 1, false);
-}
-
 void Genesis::InitializeGlobal_harmony_symbol_description() {
   if (!FLAG_harmony_symbol_description) return;
 
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index 4bdf41e9ce..3658aa9f0f 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -234,7 +234,6 @@ DEFINE_IMPLICATION(harmony_private_methods, harmony_private_fields)
   V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")                    \
   V(harmony_import_meta, "harmony import.meta property")                       \
   V(harmony_dynamic_import, "harmony dynamic import")                          \
-  V(harmony_array_flat, "harmony Array.prototype.{flat,flatMap}")              \
   V(harmony_symbol_description, "harmony Symbol.prototype.description")        \
   V(harmony_global, "harmony global")                                          \
   V(harmony_json_stringify, "well-formed JSON.stringify")                      \
diff --git a/test/mjsunit/harmony/array-flat-species.js b/test/mjsunit/harmony/array-flat-species.js
index d04f8a0875..7181c10bea 100644
--- a/test/mjsunit/harmony/array-flat-species.js
+++ b/test/mjsunit/harmony/array-flat-species.js
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-array-flat
-
 {
   class MyArray extends Array {
     static get [Symbol.species]() {
diff --git a/test/mjsunit/harmony/array-flat.js b/test/mjsunit/harmony/array-flat.js
index 86571e8dce..9a291dc3b0 100644
--- a/test/mjsunit/harmony/array-flat.js
+++ b/test/mjsunit/harmony/array-flat.js
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-array-flat
-
 assertEquals(Array.prototype.flat.length, 0);
 assertEquals(Array.prototype.flat.name, 'flat');
 
diff --git a/test/mjsunit/harmony/array-flatMap-species.js b/test/mjsunit/harmony/array-flatMap-species.js
index d4159b4801..48f9bea2d0 100644
--- a/test/mjsunit/harmony/array-flatMap-species.js
+++ b/test/mjsunit/harmony/array-flatMap-species.js
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-array-flat
-
 {
   class MyArray extends Array {
     static get [Symbol.species]() {
diff --git a/test/mjsunit/harmony/array-flatMap.js b/test/mjsunit/harmony/array-flatMap.js
index 9f0426fe7f..65a4025603 100644
--- a/test/mjsunit/harmony/array-flatMap.js
+++ b/test/mjsunit/harmony/array-flatMap.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-array-flat --allow-natives-syntax
+// Flags: --allow-natives-syntax
 
 assertEquals(Array.prototype.flatMap.length, 1);
 assertEquals(Array.prototype.flatMap.name, 'flatMap');
diff --git a/test/test262/testcfg.py b/test/test262/testcfg.py
index fe130665f6..8bec9965e2 100644
--- a/test/test262/testcfg.py
+++ b/test/test262/testcfg.py
@@ -46,8 +46,6 @@ FEATURE_FLAGS = {
   'class-static-fields-public': '--harmony-class-fields',
   'class-fields-private': '--harmony-private-fields',
   'class-static-fields-private': '--harmony-private-fields',
-  'Array.prototype.flat': '--harmony-array-flat',
-  'Array.prototype.flatMap': '--harmony-array-flat',
   'String.prototype.matchAll': '--harmony-string-matchall',
   'Symbol.matchAll': '--harmony-string-matchall',
   'numeric-separator-literal': '--harmony-numeric-separator',