diff --git a/netgen/site-bundle/3.1/manifest.json b/netgen/site-bundle/3.1/manifest.json
index 3d34b3a..848db79 100644
--- a/netgen/site-bundle/3.1/manifest.json
+++ b/netgen/site-bundle/3.1/manifest.json
@@ -4,5 +4,12 @@
     },
     "copy-from-recipe": {
         "config/": "%CONFIG_DIR%/"
+    },
+    "env": {
+        "#1": "Defines which config files will be loaded from config/app/server folder",
+        "SERVER_ENVIRONMENT": "dev",
+        "#2": "",
+        "#3": "Empty string for API key means that MailerLite newsletter integration is disabled",
+        "MAILER_LITE_API_KEY": ""
     }
 }