diff --git a/src/vs/workbench/api/electron-browser/mainThreadErrors.ts b/src/vs/workbench/api/electron-browser/mainThreadErrors.ts
index a1ff2a2dd6cf164cc0eb0ecea5c87d54f46a4722..6c283a0d98c2b6baabcd2c61fd93cc352c09a4f6 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadErrors.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadErrors.ts
@@ -16,7 +16,7 @@ export class MainThreadErrors implements MainThreadErrorsShape {
 	}
 
 	$onUnexpectedError(err: any | SerializedError): void {
-		if (err.$isError) {
+		if (err && err.$isError) {
 			const { name, message, stack } = err;
 			err = new Error();
 			err.message = message;