diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 6b357628f33..f11c88b2a0b 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -536,7 +536,7 @@ namespace ts {
 
         export function parseSourceFile(fileName: string, _sourceText: string, languageVersion: ScriptTarget, _syntaxCursor: IncrementalParser.SyntaxCursor, setParentNodes?: boolean, scriptKind?: ScriptKind): SourceFile {
 
-            const isJavaScriptFile = hasJavaScriptFileExtension(fileName) || _sourceText.lastIndexOf("// @language=javascript", 0) === 0 || scriptKind == ScriptKind.Js;
+            const isJavaScriptFile = hasJavaScriptFileExtension(fileName) || _sourceText.lastIndexOf("// @language=javascript", 0) === 0 || scriptKind == ScriptKind.JS;
 
             initializeState(fileName, _sourceText, languageVersion, isJavaScriptFile, _syntaxCursor);
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index d9613191c48..8c9d1d1d40a 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2462,10 +2462,10 @@ namespace ts {
 
     export const enum ScriptKind {
         Unknown = 0,
-        Js = 1,
-        Jsx = 2,
-        Ts = 3,
-        Tsx = 4
+        JS = 1,
+        JSX = 2,
+        TS = 3,
+        TSX = 4
     }
 
     export const enum ScriptTarget {
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index 4bc5386252f..9761afc9034 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -183,7 +183,7 @@ namespace Harness.LanguageService {
             const script = this.getScriptInfo(fileName);
             return script ? new ScriptSnapshot(script) : undefined;
         }
-        getScriptKind(fileName: string): ScriptKind { return ScriptKind.Unknown; }
+        getScriptKind(fileName: string): ts.ScriptKind { return ts.ScriptKind.Unknown; }
         getScriptVersion(fileName: string): string {
             const script = this.getScriptInfo(fileName);
             return script ? script.version.toString() : undefined;
@@ -254,7 +254,7 @@ namespace Harness.LanguageService {
             const nativeScriptSnapshot = this.nativeHost.getScriptSnapshot(fileName);
             return nativeScriptSnapshot && new ScriptSnapshotProxy(nativeScriptSnapshot);
         }
-        getScriptKind(fileName: string): ScriptKind { return this.nativeHost.getScriptKind(fileName); }
+        getScriptKind(fileName: string): ts.ScriptKind { return this.nativeHost.getScriptKind(fileName); }
         getScriptVersion(fileName: string): string { return this.nativeHost.getScriptVersion(fileName); }
         getLocalizedDiagnosticMessages(): string { return JSON.stringify({}); }
 
diff --git a/src/services/services.ts b/src/services/services.ts
index 2fa6031924c..5a5f4da607e 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1019,7 +1019,7 @@ namespace ts {
         getNewLine?(): string;
         getProjectVersion?(): string;
         getScriptFileNames(): string[];
-        getScriptKind(fileName: string): ScriptKind;
+        getScriptKind?(fileName: string): ScriptKind;
         getScriptVersion(fileName: string): string;
         getScriptSnapshot(fileName: string): IScriptSnapshot;
         getLocalizedDiagnosticMessages?(): any;
@@ -1750,7 +1750,7 @@ namespace ts {
 
         private createEntry(fileName: string, path: Path) {
             let entry: HostFileInformation;
-            const scriptKind = this.host.getScriptKind(fileName);
+            const scriptKind = this.host.getScriptKind ? this.host.getScriptKind(fileName) : ScriptKind.Unknown;
             const scriptSnapshot = this.host.getScriptSnapshot(fileName);
             if (scriptSnapshot) {
                 entry = {
@@ -1823,7 +1823,7 @@ namespace ts {
                 throw new Error("Could not find file: '" + fileName + "'.");
             }
 
-            const scriptKind = this.host.getScriptKind(fileName);
+            const scriptKind = this.host.getScriptKind ? this.host.getScriptKind(fileName) : ScriptKind.Unknown;
             const version = this.host.getScriptVersion(fileName);
             let sourceFile: SourceFile;
 
diff --git a/src/services/shims.ts b/src/services/shims.ts
index d7cf4da50fd..571c75482bb 100644
--- a/src/services/shims.ts
+++ b/src/services/shims.ts
@@ -55,7 +55,7 @@ namespace ts {
 
         /** Returns a JSON-encoded value of the type: string[] */
         getScriptFileNames(): string;
-        getScriptKind(fileName: string): ScriptKind;
+        getScriptKind?(fileName: string): ScriptKind;
         getScriptVersion(fileName: string): string;
         getScriptSnapshot(fileName: string): ScriptSnapshotShim;
         getLocalizedDiagnosticMessages(): string;
@@ -350,7 +350,8 @@ namespace ts {
         public getScriptKind(fileName: string): ScriptKind {
             try {
                 return this.shimHost.getScriptKind(fileName);
-            } catch (e) {
+            }
+            catch (e) {
                 return ScriptKind.Unknown;
             }
         }