diff --git a/aos/configuration.cc b/aos/configuration.cc
index 43e44f2..f379166 100644
--- a/aos/configuration.cc
+++ b/aos/configuration.cc
@@ -458,11 +458,16 @@
 }
 
 FlatbufferDetachedBuffer<Configuration> MergeWithConfig(
+    const Configuration *config, const Flatbuffer<Configuration> &addition) {
+  return MergeConfiguration(MergeFlatBuffers(config, &addition.message()));
+}
+
+FlatbufferDetachedBuffer<Configuration> MergeWithConfig(
     const Configuration *config, std::string_view json) {
   FlatbufferDetachedBuffer<Configuration> addition =
       JsonToFlatbuffer(json, Configuration::MiniReflectTypeTable());
 
-  return MergeConfiguration(MergeFlatBuffers(config, &addition.message()));
+  return MergeWithConfig(config, addition);
 }
 
 const Channel *GetChannel(const Configuration *config, std::string_view name,