diff --git a/contrib/visveg/vegind.py b/contrib/visveg/vegind.py
index e5966fb3..62554657 100644
--- a/contrib/visveg/vegind.py
+++ b/contrib/visveg/vegind.py
@@ -17,7 +17,8 @@ try:
     typ = sys.argv[2]
     (fileRoot, fileExt) = os.path.splitext(file)
     outFileName = fileRoot + "_" + typ + fileExt
-    isinstance(typ, ['vari', 'tgi', 'ngrdi'])
+    if typ not in ['vari', 'tgi', 'ngrdi']:
+        raise IndexError
 except (TypeError, IndexError, NameError):
     print bcolors.FAIL + 'Arguments messed up. Check arguments order and index name' + bcolors.ENDC
     print 'Usage: ./vegind.py orto index'