diff --git a/loopy/kernel/function_interface.py b/loopy/kernel/function_interface.py
index 852b9ee1d7d1e9691f7d4cc457cf30ddf717c230..eb63d364c95e6d2393fdecb174b0067c2c5ae5ec 100644
--- a/loopy/kernel/function_interface.py
+++ b/loopy/kernel/function_interface.py
@@ -682,7 +682,7 @@ class ScopedFunctionNameChanger(RuleAwareIdentityMapper):
                         ScopedFunction(self.expr_to_new_names[expr]),
                         tuple(self.rec(child)
                             for child in expr.parameters))
-            elif expanded_expr in self.expr_to_names:
+            elif expanded_expr in self.expr_to_new_names:
                 return type(expr)(
                         ScopedFunction(self.expr_to_new_names[expanded_expr]),
                         tuple(self.rec(child)
@@ -703,7 +703,7 @@ class ScopedFunctionNameChanger(RuleAwareIdentityMapper):
                     (key, self.rec(val, expn_state))
                     for key, val in six.iteritems(expr.kw_parameters))
                     )
-        elif expanded_expr in self.expr_to_names:
+        elif expanded_expr in self.expr_to_new_names:
             return type(expr)(
                 ScopedFunction(self.expr_to_new_names[expanded_expr]),
                 tuple(self.rec(child, expn_state)