diff --git a/src/gridtk/tools.py b/src/gridtk/tools.py
index d1e4f3a774c0b65ed0bf9879b7277a0f6c6b137c..9ece928aeeb6f6ea470059271f7e2c6eb8e9b858 100644
--- a/src/gridtk/tools.py
+++ b/src/gridtk/tools.py
@@ -232,7 +232,7 @@ def qsub(
             except ValueError:
                 # must be complete...
                 scmd.append("%s" % array)
-        if isinstance(array, (str, bytes)):
+        if isinstance(array, int):
             scmd.append("1-%d:1" % array)
         if isinstance(array, (tuple, list)):
             if len(array) < 1 or len(array) > 3: