diff --git a/cal_tools/cal_tools/ana_tools.py b/cal_tools/cal_tools/ana_tools.py
index 804a16b42b6db00cc6dbf9ea0dc47d64c0a488b1..f58ace59b07e4fc43e127bf7695d19444bb37f85 100644
--- a/cal_tools/cal_tools/ana_tools.py
+++ b/cal_tools/cal_tools/ana_tools.py
@@ -170,7 +170,8 @@ def combine_lists(*args, names=None):
     for param in params:
         possible_params = [x + [y] for x in possible_params for y in param]
 
-    if isinstance(names, list) and len(names)==len(args):
+    if isinstance(names, (list, tuple)):
+        assert len(names) == len(args)
         d_possible_params = []
         for par in possible_params:
             d_possible_params.append(dict(zip(names, par)))