diff --git a/neocalc.py b/neocalc.py
index 2f1f5c1b38fa5097400fbe95b3f5ffacdbc88aea..3c4576a0c1014a5d71e0aca962dba49f93466d2d 100755
--- a/neocalc.py
+++ b/neocalc.py
@@ -112,7 +112,11 @@ def apply(stack,obj):
     return stack
 
 class Cli(Cmd):
-    mkprompt = lambda s: s + ' > '
+    # named lambdas are not alright
+    @staticmethod
+    def mkprompt(s):
+        return s + ' > '
+
     prompt = mkprompt('')
     stack,future = [],[]