diff --git a/src/vs/base/common/worker/workerClient.ts b/src/vs/base/common/worker/workerClient.ts
index 61fef76290dc7..86a5676b3305d 100644
--- a/src/vs/base/common/worker/workerClient.ts
+++ b/src/vs/base/common/worker/workerClient.ts
@@ -227,7 +227,9 @@ export class WorkerClient {
 	}
 
 	private _postMessage(msg:any): void {
-		this._worker.postMessage(stringify(msg));
+		if (this._worker) {
+			this._worker.postMessage(stringify(msg));
+		}
 	}
 
 	private _onSerializedMessage(msg:string): void {
diff --git a/src/vs/base/worker/defaultWorkerFactory.ts b/src/vs/base/worker/defaultWorkerFactory.ts
index abfa5b9935c02..36dc060d5d2ef 100644
--- a/src/vs/base/worker/defaultWorkerFactory.ts
+++ b/src/vs/base/worker/defaultWorkerFactory.ts
@@ -41,7 +41,9 @@ class WebWorker implements IWorker {
 	}
 
 	public postMessage(msg:string): void {
-		this.worker.postMessage(msg);
+		if (this.worker) {
+			this.worker.postMessage(msg);
+		}
 	}
 
 	public dispose(): void {