diff --git a/ysh/expr_eval.py b/ysh/expr_eval.py
index 3b034dce88..692bfee8d6 100644
--- a/ysh/expr_eval.py
+++ b/ysh/expr_eval.py
@@ -367,7 +367,7 @@ def CallConvertFunc(self, func_val, arg):
             # TODO: Use logic from _EvalFuncCall
 
             #val = func_proc.CallUserFunc(func_val, rd, self.mem, self.cmd_ev)
-            val = None
+            val = value.Null
 
         return val