diff --git a/src/vs/workbench/api/common/extHostWorkspace.ts b/src/vs/workbench/api/common/extHostWorkspace.ts
index 3c176107270..a36bcf43346 100644
--- a/src/vs/workbench/api/common/extHostWorkspace.ts
+++ b/src/vs/workbench/api/common/extHostWorkspace.ts
@@ -288,7 +288,7 @@ export class ExtHostWorkspace implements ExtHostWorkspaceShape, IExtHostWorkspac
 				this._unconfirmedWorkspace = undefined;
 
 				// show error to user
-				this._messageService.$showMessage(Severity.Error, localize('updateerror', "Extension '{0}' failed to update workspace folders: {1}", extName, error), { extension }, []);
+				this._messageService.$showMessage(Severity.Error, localize('updateerror', "Extension '{0}' failed to update workspace folders: {1}", extName, error.toString()), { extension }, []);
 			});
 		}