diff --git a/gnuviechadmin/backend/sysuser.py b/gnuviechadmin/backend/sysuser.py
index 0b65529..ff58bcb 100644
--- a/gnuviechadmin/backend/sysuser.py
+++ b/gnuviechadmin/backend/sysuser.py
@@ -50,14 +50,18 @@ class SysuserEntity(BackendEntity):
 
     def _get_next_sysusername(self):
         prefix = config.get('sysuser', 'nameprefix')
+        self.logger.debug("looking for next user with prefix %s" % (prefix))
         usernames = [user.username for user in \
                      getenttools.find_user_by_prefix(prefix)]
-        maxid = max([int(username[len(prefix):]) for username in usernames])
-        maxid += 2
-        for number in range(1, maxid):
-            username = "%s%02d" % (prefix, number)
-            if not username in usernames:
-                return username
+        if usernames:
+            maxid = max([int(username[len(prefix):]) for username in usernames])
+            maxid += 2
+            for number in range(1, maxid):
+                username = "%s%02d" % (prefix, number)
+                if not username in usernames:
+                    return username
+        else:
+            return "%s%02d" % (prefix, 1)
 
     def _get_default_sysusertype(self):
         return 1