diff --git a/src/vs/workbench/api/common/extHostWebview.ts b/src/vs/workbench/api/common/extHostWebview.ts
index fb648338fe6..a898dbba4fc 100644
--- a/src/vs/workbench/api/common/extHostWebview.ts
+++ b/src/vs/workbench/api/common/extHostWebview.ts
@@ -389,7 +389,7 @@ class WebviewDocumentStore {
 	}
 
 	private key(viewType: string, resource: vscode.Uri): string {
-		return `${viewType}@@@${resource.toString}`;
+		return `${viewType}@@@${resource}`;
 	}
 }