diff --git a/src/vs/base/common/errors.ts b/src/vs/base/common/errors.ts
index 568a6baee1adb..18d8cad519c8f 100644
--- a/src/vs/base/common/errors.ts
+++ b/src/vs/base/common/errors.ts
@@ -152,6 +152,15 @@ export function onUnexpectedPromiseError<T>(promise: TPromise<T>): TPromise<T |
 	return promise.then(null, onUnexpectedError);
 }
 
+export interface SerializedError {
+	readonly $isError: true;
+	readonly name: string;
+	readonly message: string;
+	readonly stack: string;
+}
+
+export function transformErrorForSerialization(error: Error): SerializedError;
+export function transformErrorForSerialization(error: any): any;
 export function transformErrorForSerialization(error: any): any {
 	if (error instanceof Error) {
 		let { name, message } = error;
diff --git a/src/vs/workbench/api/electron-browser/mainThreadErrors.ts b/src/vs/workbench/api/electron-browser/mainThreadErrors.ts
index c2ee7a0baa256..25ee026c2b19f 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadErrors.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadErrors.ts
@@ -14,7 +14,14 @@ export class MainThreadErrors implements MainThreadErrorsShape {
 	public dispose(): void {
 	}
 
-	public $onUnexpectedExtHostError(err: any): void {
+	public $onUnexpectedExtHostError(err: any | errors.SerializedError): void {
+		if (err.$isError) {
+			const { name, message, stack } = err;
+			err = new Error();
+			err.name = name;
+			err.message = message;
+			err.stack = stack;
+		}
 		errors.onUnexpectedError(err);
 	}
 }