diff --git a/lib/vscode/test/ui/splitview/package.json b/lib/vscode/test/ui/splitview/package.json
index d6ce0c37374c..b2548d0fbe9b 100644
--- a/lib/vscode/test/ui/splitview/package.json
+++ b/lib/vscode/test/ui/splitview/package.json
@@ -5,7 +5,7 @@
   "license": "MIT",
   "devDependencies": {
     "koa": "^2.5.1",
-    "koa-mount": "^3.0.0",
+    "koa-mount": "^4.0.0",
     "koa-route": "^3.2.0",
     "koa-static": "^5.0.0",
     "mz": "^2.7.0"