diff --git a/mkexp b/mkexp
index 09cc1c3a4375866318f3a8b16cd88d14ff9bbe1e..c46462178f1baf794917fef7ab95fb39f72782e7 100755
--- a/mkexp
+++ b/mkexp
@@ -550,7 +550,8 @@ for subjob, subconfig in jobs_config.items():
         del subconfig
 
         # Extend all namelists
-        for namelist, groups in job_config['namelists'].items():
+        for namelist in job_config['namelists'].sections:
+            groups = job_config['namelists'][namelist]
             extended_groups = set()
             for group in groups.sections:
                 extend(group, groups, extended_groups)