diff --git a/reclass_tools/walk_models.py b/reclass_tools/walk_models.py
index 024b3cf..8027273 100644
--- a/reclass_tools/walk_models.py
+++ b/reclass_tools/walk_models.py
@@ -164,7 +164,9 @@
                     if _param:
                         for key, val in _param.items():
                             if key in _params:
+                                # Keep list values sorted
                                 _params[key].append(val)
+                                _params[key] = sorted(_params[key])
                             else:
                                 _params[key] = [val]
     return _params