diff --git a/reviews.py b/reviews.py
index b899de2..8cf414c 100644
--- a/reviews.py
+++ b/reviews.py
@@ -36,7 +36,7 @@ COMMANDS = {
 
 
 def main():
-    if sys.argv[1] not in COMMANDS:
+    if len(sys.argv) < 2 or sys.argv[1] not in COMMANDS:
         print("Invalid command")
         exit(2)