diff --git a/src/vs/workbench/common/resources.ts b/src/vs/workbench/common/resources.ts
index 34b7d02d84699..ec82d07b99be6 100644
--- a/src/vs/workbench/common/resources.ts
+++ b/src/vs/workbench/common/resources.ts
@@ -23,11 +23,13 @@ export class ResourceContextKey implements IContextKey<URI> {
 	static Filename = new RawContextKey<string>('resourceFilename', undefined);
 	static LangId = new RawContextKey<string>('resourceLangId', undefined);
 	static Resource = new RawContextKey<URI>('resource', undefined);
+	static Extension = new RawContextKey<string>('resourceExtname', undefined);
 
 	private _resourceKey: IContextKey<URI>;
 	private _schemeKey: IContextKey<string>;
 	private _filenameKey: IContextKey<string>;
 	private _langIdKey: IContextKey<string>;
+	private _extensionKey: IContextKey<string>;
 
 	constructor(
 		@IContextKeyService contextKeyService: IContextKeyService,
@@ -37,6 +39,7 @@ export class ResourceContextKey implements IContextKey<URI> {
 		this._filenameKey = ResourceContextKey.Filename.bindTo(contextKeyService);
 		this._langIdKey = ResourceContextKey.LangId.bindTo(contextKeyService);
 		this._resourceKey = ResourceContextKey.Resource.bindTo(contextKeyService);
+		this._extensionKey = ResourceContextKey.Extension.bindTo(contextKeyService);
 	}
 
 	set(value: URI) {
@@ -44,12 +47,14 @@ export class ResourceContextKey implements IContextKey<URI> {
 		this._schemeKey.set(value && value.scheme);
 		this._filenameKey.set(value && basename(value.fsPath));
 		this._langIdKey.set(value && this._modeService.getModeIdByFilenameOrFirstLine(value.fsPath));
+		this._extensionKey.set(value && paths.extname(value.fsPath));
 	}
 
 	reset(): void {
 		this._schemeKey.reset();
 		this._langIdKey.reset();
 		this._resourceKey.reset();
+		this._extensionKey.reset();
 	}
 
 	public get(): URI {