diff --git a/tools/dom/scripts/systemhtml.py b/tools/dom/scripts/systemhtml.py
index c8ff6b3118f..20a25ed9033 100644
--- a/tools/dom/scripts/systemhtml.py
+++ b/tools/dom/scripts/systemhtml.py
@@ -2002,7 +2002,7 @@ class Dart2JSBackend(HtmlDartGenerator):
                 '  $RENAME$METADATA$MODIFIERS$TYPE $NAME($PARAMS) => '\
                 'js_util.callMethod(this, \'$JSNAME\', [$ARGS]);\n'
                 if CanUseStaticExtensions(self._interface_name, self._generate_static_extensions) else
-                '  $RENAME$METADATA$MODIFIERS$TYPE $NAME($PARAMS) native;\n',
+                '\n  $RENAME$METADATA$MODIFIERS$TYPE $NAME($PARAMS) native;\n',
                 RENAME=self._RenamingAnnotation(info.declared_name, html_name),
                 METADATA=self._Metadata(
                     info.type_name, info.declared_name,
diff --git a/tools/dom/templates/dart2js_static_extension_impl.darttemplate b/tools/dom/templates/dart2js_static_extension_impl.darttemplate
index e2b3c614cff..5501eee3e08 100644
--- a/tools/dom/templates/dart2js_static_extension_impl.darttemplate
+++ b/tools/dom/templates/dart2js_static_extension_impl.darttemplate
@@ -1,10 +1,11 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
-$(ANNOTATIONS)@sealed$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$MIXINS$IMPLEMENTS { $!CLASSMEMBERS }
+//todo: add @sealed annotation
+$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$MIXINS$IMPLEMENTS { $!CLASSMEMBERS }
 
 extension $(CLASSNAME)Extension on $CLASSNAME {
 $!EXTENSIONMEMBERS
diff --git a/tools/dom/templates/html/dart2js/html_dart2js.darttemplate b/tools/dom/templates/html/dart2js/html_dart2js.darttemplate
index 1559461ff4d..d1e9e6baa9f 100644
--- a/tools/dom/templates/html/dart2js/html_dart2js.darttemplate
+++ b/tools/dom/templates/html/dart2js/html_dart2js.darttemplate
@@ -52,6 +52,7 @@ import 'dart:_interceptors' show
     getNativeInterceptor,
     setDispatchProperty;
 import 'dart:_foreign_helper' show JS, JS_INTERCEPTOR_CONSTANT;
+import 'dart:js_util' as js_util;
 
 export 'dart:_internal' show HttpStatus;
 export 'dart:html_common' show promiseToFuture;