diff --git a/loopy/translation_unit.py b/loopy/translation_unit.py
index 6fe3e7171..93ecbe9ab 100644
--- a/loopy/translation_unit.py
+++ b/loopy/translation_unit.py
@@ -302,9 +302,9 @@ def with_kernel(self, kernel: LoopKernel) -> Self:
             # update the callable kernel
             new_in_knl_callable = self.callables_table[kernel.name].copy(
                     subkernel=kernel)
-            new_callables = self.callables_table.mutate()
-            new_callables[kernel.name] = new_in_knl_callable
-            return self.copy(callables_table=new_callables.finish())
+            return self.copy(
+                callables_table=self.callables_table.set(
+                                        kernel.name, new_in_knl_callable))
         else:
             # add a new callable kernel
             clbl = CallableKernel(kernel)