diff --git a/src/dynapyt/runtime.py b/src/dynapyt/runtime.py
index 2fede47..df67759 100644
--- a/src/dynapyt/runtime.py
+++ b/src/dynapyt/runtime.py
@@ -95,6 +95,8 @@ def filtered(self, func, f, args):
             return False
         if len(args) > 0:
             sub_args = args
+        else:
+            sub_args = []
         sub_arg_names = []
         for arg in sub_args:
             if (