diff --git a/src/vs/workbench/api/node/extHostCLIServer.ts b/src/vs/workbench/api/node/extHostCLIServer.ts
index 9ae6f7b379b..5a48881f9b4 100644
--- a/src/vs/workbench/api/node/extHostCLIServer.ts
+++ b/src/vs/workbench/api/node/extHostCLIServer.ts
@@ -171,7 +171,7 @@ export class CLIServerBase {
 			res.write(output);
 		} catch (e) {
 			res.writeHead(500);
-			res.write(toString());
+			res.write(String(e));
 		}
 		res.end();
 	}