diff --git a/fsl/scripts/fsl_convert_x5.py b/fsl/scripts/fsl_convert_x5.py
index 216ea308a18dae7fd1267da0ff5b3c1ea754b9f6..13a279456c623a9fc9623741302a5bf3957e9e20 100644
--- a/fsl/scripts/fsl_convert_x5.py
+++ b/fsl/scripts/fsl_convert_x5.py
@@ -81,8 +81,6 @@ def parseArgs(args):
     if len(args) == 1:
         if   args[0] == 'flirt': flirt.print_help()
         elif args[0] == 'fnirt': fnirt.print_help()
-        else: parser.error('Unknown sub-command: {}'.format(args[0]))
-        sys.exit(0)
 
     args = parser.parse_args(args)