diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/workspace.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/workspace.test.ts
index a350f5334e2..41305d076b2 100644
--- a/extensions/vscode-api-tests/src/singlefolder-tests/workspace.test.ts
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/workspace.test.ts
@@ -520,6 +520,16 @@ suite('workspace-namespace', () => {
 		assert.equal(vscode.workspace.asRelativePath(results[0].uri), '10linefile.ts');
 	});
 
+	test('findTextInFiles, cancellation', async () => {
+		const results: vscode.TextSearchResult[] = [];
+		const cancellation = new vscode.CancellationTokenSource();
+		cancellation.cancel();
+
+		await vscode.workspace.findTextInFiles({ pattern: 'foo' }, result => {
+			results.push(result);
+		}, cancellation.token);
+	});
+
 	test('applyEdit', () => {
 
 		return vscode.workspace.openTextDocument(vscode.Uri.parse('untitled:' + join(vscode.workspace.rootPath || '', './new2.txt'))).then(doc => {
diff --git a/src/vs/workbench/api/electron-browser/mainThreadWorkspace.ts b/src/vs/workbench/api/electron-browser/mainThreadWorkspace.ts
index 8db9fa2331f..c43f1982a74 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadWorkspace.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadWorkspace.ts
@@ -172,29 +172,29 @@ export class MainThreadWorkspace implements MainThreadWorkspaceShape {
 		const queryBuilder = this._instantiationService.createInstance(QueryBuilder);
 		const query = queryBuilder.text(pattern, folders, options);
 
-		return new TPromise((resolve, reject) => {
-			const onProgress = (p: ISearchProgressItem) => {
-				if (p.lineMatches) {
-					this._proxy.$handleTextSearchResult(p, requestId);
+		const onProgress = (p: ISearchProgressItem) => {
+			if (p.lineMatches) {
+				this._proxy.$handleTextSearchResult(p, requestId);
+			}
+		};
+
+		const search = this._searchService.search(query, onProgress).then(
+			() => {
+				delete this._activeSearches[requestId];
+				return null;
+			},
+			err => {
+				delete this._activeSearches[requestId];
+				if (!isPromiseCanceledError(err)) {
+					return TPromise.wrapError(err);
 				}
-			};
 
-			const search = this._searchService.search(query, onProgress).then(
-				() => {
-					delete this._activeSearches[requestId];
-					resolve(null);
-				},
-				err => {
-					delete this._activeSearches[requestId];
-					if (!isPromiseCanceledError(err)) {
-						reject(TPromise.wrapError(err));
-					}
+				return undefined;
+			});
 
-					return undefined;
-				});
+		this._activeSearches[requestId] = search;
 
-			this._activeSearches[requestId] = search;
-		});
+		return search;
 	}
 
 	$cancelSearch(requestId: number): Thenable<boolean> {
diff --git a/src/vs/workbench/api/node/extHostWorkspace.ts b/src/vs/workbench/api/node/extHostWorkspace.ts
index ae1f6739927..13de47ac058 100644
--- a/src/vs/workbench/api/node/extHostWorkspace.ts
+++ b/src/vs/workbench/api/node/extHostWorkspace.ts
@@ -395,7 +395,13 @@ export class ExtHostWorkspace implements ExtHostWorkspaceShape {
 			excludePattern: options.exclude && globPatternToString(options.exclude)
 		};
 
+		let isCanceled = false;
+
 		this._activeSearchCallbacks[requestId] = p => {
+			if (isCanceled) {
+				return;
+			}
+
 			p.lineMatches.forEach(lineMatch => {
 				lineMatch.offsetAndLengths.forEach(offsetAndLength => {
 					const range = new Range(lineMatch.lineNumber, offsetAndLength[0], lineMatch.lineNumber, offsetAndLength[0] + offsetAndLength[1]);
@@ -409,7 +415,10 @@ export class ExtHostWorkspace implements ExtHostWorkspaceShape {
 		};
 
 		if (token) {
-			token.onCancellationRequested(() => this._proxy.$cancelSearch(requestId));
+			token.onCancellationRequested(() => {
+				isCanceled = true;
+				this._proxy.$cancelSearch(requestId);
+			});
 		}
 
 		return this._proxy.$startTextSearch(query, queryOptions, requestId).then(