diff --git a/pkg/analyzer/lib/src/dart/sdk/patch.dart b/pkg/analyzer/lib/src/dart/sdk/patch.dart
index f6b8a3bdb35..88a122eecf2 100644
--- a/pkg/analyzer/lib/src/dart/sdk/patch.dart
+++ b/pkg/analyzer/lib/src/dart/sdk/patch.dart
@@ -21,6 +21,7 @@ import 'package:path/src/context.dart';
  * [SdkPatcher] applies patches to SDK [CompilationUnit].
  */
 class SdkPatcher {
+  bool _allowNewPublicNames;
   String _baseDesc;
   String _patchDesc;
   CompilationUnit _patchUnit;
@@ -46,8 +47,10 @@ class SdkPatcher {
             'The URI of the unit to patch must have the "dart" scheme: $uri');
       }
       List<String> uriSegments = uri.pathSegments;
-      libraryUriStr = 'dart:${uriSegments.first}';
+      String libraryName = uriSegments.first;
+      libraryUriStr = 'dart:$libraryName';
       isLibraryDefiningUnit = uriSegments.length == 1;
+      _allowNewPublicNames = libraryName == '_internal';
     }
     // Prepare the patch files to apply.
     List<String> patchPaths;
@@ -90,6 +93,9 @@ class SdkPatcher {
   }
 
   void _failIfPublicName(AstNode node, String name) {
+    if (_allowNewPublicNames) {
+      return;
+    }
     if (!Identifier.isPrivateName(name)) {
       _failInPatch('contains a public declaration "$name"', node.offset);
     }
@@ -121,9 +127,9 @@ class SdkPatcher {
               patchMember.offset);
         }
         String name = fields[0].name.name;
-        if (!Identifier.isPrivateName(className) &&
+        if (!_allowNewPublicNames &&
+            !Identifier.isPrivateName(className) &&
             !Identifier.isPrivateName(name)) {
-          // TODO(scheglov) allow adding public fields into dart:_internal
           _failInPatch('contains a public field', patchMember.offset);
         }
         membersToAppend.add(patchMember);
@@ -206,7 +212,7 @@ class SdkPatcher {
           }
         } else {
           if (name == null) {
-            if (!Identifier.isPrivateName(className)) {
+            if (!_allowNewPublicNames && !Identifier.isPrivateName(className)) {
               _failInPatch(
                   'contains an unnamed public constructor', patchMember.offset);
             }
diff --git a/pkg/analyzer/test/src/dart/sdk/patch_test.dart b/pkg/analyzer/test/src/dart/sdk/patch_test.dart
index 6f3d34609bb..dc3a9034f6a 100644
--- a/pkg/analyzer/test/src/dart/sdk/patch_test.dart
+++ b/pkg/analyzer/test/src/dart/sdk/patch_test.dart
@@ -279,7 +279,7 @@ class A {
     }, throwsArgumentError);
   }
 
-  test_class_field_append_publiInPrivateClass() {
+  test_class_field_append_publicInPrivateClass() {
     CompilationUnit unit = _doTopLevelPatching(
         r'''
 class _C {
@@ -480,6 +480,47 @@ final Map<String, LibraryInfo> LIBRARIES = const <String, LibraryInfo> {
     }, throwsArgumentError);
   }
 
+  test_internal_allowNewPublicNames() {
+    _setSdkLibraries(r'''
+final Map<String, LibraryInfo> LIBRARIES = const <String, LibraryInfo> {
+  '_internal' : const LibraryInfo(
+    'internal/internal.dart',
+    patches: {VM_PLATFORM: ['internal/internal_patch.dart']}),
+};''');
+    File file = provider.newFile(
+        _p('/sdk/lib/internal/internal.dart'),
+        r'''
+library dart._internal;
+class A {}
+class B {
+  B();
+}
+''');
+    provider.newFile(
+        _p('/sdk/lib/internal/internal_patch.dart'),
+        r'''
+@patch
+class B {
+  int newField;
+  B.newConstructor();
+  int newMethod() => 1;
+}
+class NewClass {}
+int newFunction() => 2;
+''');
+
+    _createSdk();
+
+    Source source = file.createSource(FastUri.parse('dart:_internal'));
+    CompilationUnit unit = SdkPatcher.parse(source, true, listener);
+    patcher.patch(sdk, SdkLibraryImpl.VM_PLATFORM, listener, source, unit);
+    _assertUnitCode(
+        unit,
+        'library dart._internal; class A {} '
+        'class B {B(); int newField; B.newConstructor(); int newMethod() => 1;} '
+        'class NewClass {} int newFunction() => 2;');
+  }
+
   test_part() {
     String baseLibCode = r'''
 library test;