diff --git a/cyber_fenneko/__init__.py b/cyber_fenneko/__init__.py
index 1eafe85..513eaa0 100644
--- a/cyber_fenneko/__init__.py
+++ b/cyber_fenneko/__init__.py
@@ -12,6 +12,10 @@ api_id = os.environ.get('APP_ID')
 api_hash = os.environ.get('APP_HASH')
 phone_number = os.environ.get('TG_PHONE')
 
+for var in [api_id, api_hash, phone_number]:
+    if not var:
+        raise ValueError('Environment variable not set')
+
 session = SQLiteSession('fenneko-' + phone_number)
 client = TelegramClient(session, api_id, api_hash)