diff --git a/README.md b/README.md
index 1b1e404..4a5e59d 100644
--- a/README.md
+++ b/README.md
@@ -28,5 +28,8 @@ To build an Xcode image (don't forget to setup `FASTLANE_USER` and `FASTLANE_PAS
 [xcode-install](https://github.com/KrauseFx/xcode-install#usage)):
 
 ```bash
-packer build templates/catalina-flutter.json
+packer build -var xcode_version="11.5" \
+  -var fastalne_user="$FASTLANE_USER" \
+  -var fastlane_password="$FASTLANE_PASSWORD" \
+  templates/catalina-xcode.json
 ```
diff --git a/templates/catalina-xcode.json b/templates/catalina-xcode.json
index ff11c6d..2b2ba24 100644
--- a/templates/catalina-xcode.json
+++ b/templates/catalina-xcode.json
@@ -12,8 +12,8 @@
     }
   ],
   "variables": {
-    "fastlane_user": "{{env `FASTLANE_USER`}}",
-    "fastlane_password": "{{env `FASTLANE_PASSWORD`}}",
+    "fastlane_user": "",
+    "fastlane_password": "",
     "xcode_version": "11.5"
   },
   "provisioners": [