diff --git a/app.json b/app.json
index ac9c4bf580..e2e7786864 100644
--- a/app.json
+++ b/app.json
@@ -10,7 +10,7 @@
   },
 
   "env": {
-    "CLASSROOM_WEBHOOK_PREFIX_URL": {
+    "CLASSROOM_WEBHOOK_URL_PREFIX": {
       "description": "The URL for your application to receive webhooks ex https://classroom.github.com",
       "required": true
     },