diff --git a/km3buu/cmd.py b/km3buu/cmd.py
index c92ff71bd07cc87ada86d705c525473c3c1bb7ca..917cbe7f8543f4d4622cb995623e3962c1455a13 100755
--- a/km3buu/cmd.py
+++ b/km3buu/cmd.py
@@ -227,9 +227,9 @@ def main():
     elif args.geometry == 'can':
         kwargs = {"detector_center": tuple(args.center), "zenith": args.zenith}
         if args.dimensions:
-            kwargs["radius"] = arg.dimensions[0]
-            kwargs["zmin"] = arg.dimensions[1]
-            kwargs["zmax"] = arg.dimensions[2]
+            kwargs["radius"] = args.dimensions[0]
+            kwargs["zmin"] = args.dimensions[1]
+            kwargs["zmax"] = args.dimensions[2]
         volume = CanVolume(**kwargs)
     run_descriptor = ""
     if args.runnumber: