diff --git a/chromium/v8/src/objects/map-updater.cc b/chromium/v8/src/objects/map-updater.cc
index 047750ebbd45..1c0cb772dc0e 100644
--- a/chromium/v8/src/objects/map-updater.cc
+++ b/chromium/v8/src/objects/map-updater.cc
@@ -135,11 +135,20 @@ Handle<Map> MapUpdater::ReconfigureToDataField(InternalIndex descriptor,
   if (old_details.constness() == PropertyConstness::kConst &&
       old_details.location() == kField &&
       old_details.attributes() != new_attributes_) {
+    // Ensure we'll be updating constness of the up-to-date version of old_map_.
+    Handle<Map> old_map = Map::Update(isolate_, old_map_);
+    PropertyDetails details =
+        old_map->instance_descriptors().GetDetails(descriptor);
     Handle<FieldType> field_type(
-        old_descriptors_->GetFieldType(modified_descriptor_), isolate_);
-    Map::GeneralizeField(isolate_, old_map_, descriptor,
-                         PropertyConstness::kMutable,
-                         old_details.representation(), field_type);
+        old_map->instance_descriptors().GetFieldType(descriptor),
+        isolate_);
+    Map::GeneralizeField(isolate_, old_map, descriptor,
+                         PropertyConstness::kMutable, details.representation(),
+                         field_type);
+    DCHECK_EQ(PropertyConstness::kMutable,
+              old_map->instance_descriptors()
+                  .GetDetails(descriptor)
+                  .constness());
     // The old_map_'s property must become mutable.
     // Note, that the {old_map_} and {old_descriptors_} are not expected to be
     // updated by the generalization if the map is already deprecated.
diff --git a/chromium/v8/src/runtime/runtime-object.cc b/chromium/v8/src/runtime/runtime-object.cc
index 41dea0fe443f..b4ca17e92a4a 100644
--- a/chromium/v8/src/runtime/runtime-object.cc
+++ b/chromium/v8/src/runtime/runtime-object.cc
@@ -357,6 +357,34 @@ RUNTIME_FUNCTION(Runtime_ObjectHasOwnProperty) {
   return ReadOnlyRoots(isolate).false_value();
 }
 
+RUNTIME_FUNCTION(Runtime_HasOwnConstDataProperty) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(2, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Object, property, 1);
+
+  bool success;
+  LookupIterator::Key key(isolate, property, &success);
+  if (!success) return ReadOnlyRoots(isolate).undefined_value();
+
+  if (object->IsJSObject()) {
+    Handle<JSObject> js_obj = Handle<JSObject>::cast(object);
+    LookupIterator it(isolate, js_obj, key, js_obj, LookupIterator::OWN);
+
+    switch (it.state()) {
+      case LookupIterator::NOT_FOUND:
+        return isolate->heap()->ToBoolean(false);
+      case LookupIterator::DATA:
+        return isolate->heap()->ToBoolean(it.constness() ==
+                                          PropertyConstness::kConst);
+      default:
+        return ReadOnlyRoots(isolate).undefined_value();
+    }
+  }
+
+  return ReadOnlyRoots(isolate).undefined_value();
+}
+
 RUNTIME_FUNCTION(Runtime_AddDictionaryProperty) {
   HandleScope scope(isolate);
   Handle<JSObject> receiver = args.at<JSObject>(0);
diff --git a/chromium/v8/src/runtime/runtime.h b/chromium/v8/src/runtime/runtime.h
index 667b1f0045d8..1cf0e02ac137 100644
--- a/chromium/v8/src/runtime/runtime.h
+++ b/chromium/v8/src/runtime/runtime.h
@@ -487,6 +487,7 @@ namespace internal {
   F(HasElementsInALargeObjectSpace, 1, 1)     \
   F(HasFastElements, 1, 1)                    \
   F(HasFastProperties, 1, 1)                  \
+  F(HasOwnConstDataProperty, 2, 1)            \
   F(HasFixedBigInt64Elements, 1, 1)           \
   F(HasFixedBigUint64Elements, 1, 1)          \
   F(HasFixedFloat32Elements, 1, 1)            \