diff --git a/pkg/analysis_server/lib/src/context_manager.dart b/pkg/analysis_server/lib/src/context_manager.dart
index 2d4d08faed6..ac5bceda2a0 100644
--- a/pkg/analysis_server/lib/src/context_manager.dart
+++ b/pkg/analysis_server/lib/src/context_manager.dart
@@ -19,6 +19,7 @@ import 'package:analyzer/source/package_map_provider.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/source/path_filter.dart';
 import 'package:analyzer/source/pub_package_map_provider.dart';
+import 'package:analyzer/source/sdk_ext.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ -1352,7 +1353,8 @@ class PackageMapDisposition extends FolderDisposition {
   @override
   Iterable<UriResolver> createPackageUriResolvers(
           ResourceProvider resourceProvider) =>
-      <UriResolver>[new PackageMapUriResolver(resourceProvider, packageMap)];
+      <UriResolver>[new SdkExtUriResolver(packageMap),
+                    new PackageMapUriResolver(resourceProvider, packageMap)];
 }
 
 /**
@@ -1370,6 +1372,19 @@ class PackagesFileDisposition extends FolderDisposition {
 
   @override
   Iterable<UriResolver> createPackageUriResolvers(
-          ResourceProvider resourceProvider) =>
-      const <UriResolver>[];
+          ResourceProvider resourceProvider) {
+    if (packages != null) {
+      // Construct package map for the SdkExtUriResolver.
+      Map<String, List<Folder>> packageMap = <String, List<Folder>>{};
+      packages.asMap().forEach((String name, Uri uri) {
+        if (uri.scheme == 'file' || uri.scheme == '' /* unspecified */) {
+          var path = resourceProvider.pathContext.fromUri(uri);
+          packageMap[name] = <Folder>[resourceProvider.getFolder(path)];
+        }
+      });
+      return <UriResolver>[new SdkExtUriResolver(packageMap)];
+    } else {
+      return const <UriResolver>[];
+    }
+  }
 }
diff --git a/pkg/analysis_server/test/context_manager_test.dart b/pkg/analysis_server/test/context_manager_test.dart
index c810386b6b3..2096933c20f 100644
--- a/pkg/analysis_server/test/context_manager_test.dart
+++ b/pkg/analysis_server/test/context_manager_test.dart
@@ -344,6 +344,45 @@ analyzer:
     expect(contexts[1].name, equals('/my/proj/lib'));
   }
 
+  // TODO(paulberry): This test only tests PackagesFileDisposition.
+  // Once http://dartbug.com/23909 is fixed, add a test for sdk extensions
+  // and PackageMapDisposition.
+  test_sdk_ext_packagespec() async {
+    // Create files.
+    String libPath = newFolder([projPath, LIB_NAME]);
+    newFile([libPath, 'main.dart']);
+    newFile([libPath, 'nope.dart']);
+    String sdkExtPath = newFolder([projPath, 'sdk_ext']);
+    newFile([sdkExtPath, 'entry.dart']);
+    String sdkExtSrcPath = newFolder([projPath, 'sdk_ext', 'src']);
+    newFile([sdkExtSrcPath, 'part.dart']);
+    // Setup sdk extension mapping.
+    newFile(
+        [libPath, '_sdkext'],
+        r'''
+{
+  "dart:foobar": "../sdk_ext/entry.dart"
+}
+''');
+    // Setup .packages file
+    newFile(
+      [projPath, '.packages'],
+      r'''
+test_pack:lib/
+''');
+    // Setup context.
+    manager.setRoots(<String>[projPath], <String>[], <String, String>{});
+    // Confirm that one context was created.
+    var contexts =
+        manager.contextsInAnalysisRoot(resourceProvider.newFolder(projPath));
+    expect(contexts, isNotNull);
+    expect(contexts.length, equals(1));
+    var context = contexts[0];
+    var source = context.sourceFactory.forUri('dart:foobar');
+    expect(source.fullName, equals('/my/proj/sdk_ext/entry.dart'));
+  }
+
+
   test_refresh_folder_with_packagespec() {
     // create a context with a .packages file
     String packagespecFile = posix.join(projPath, '.packages');