diff --git a/mhcflurry/predict_command.py b/mhcflurry/predict_command.py
index 0a8e5c97a4915e66c73059d0b03d5c2ae46a8232..6d92a501233ecad182b7b83d2303ae140c2a9ef6 100644
--- a/mhcflurry/predict_command.py
+++ b/mhcflurry/predict_command.py
@@ -149,6 +149,10 @@ implementation_args.add_argument(
 
 
 def run(argv=sys.argv[1:]):
+    if not argv:
+        parser.print_help()
+        parser.exit(1)
+
     args = parser.parse_args(argv)
 
     set_keras_backend(backend=args.backend, num_threads=args.threads)