diff --git a/eval/public/containers/field_backed_map_impl.cc b/eval/public/containers/field_backed_map_impl.cc
index cd56f51..4d2a546 100644
--- a/eval/public/containers/field_backed_map_impl.cc
+++ b/eval/public/containers/field_backed_map_impl.cc
@@ -117,7 +117,9 @@ int FieldBackedMapImpl::size() const {
 const CelList* FieldBackedMapImpl::ListKeys() const { return key_list_.get(); }
 
 absl::optional<CelValue> FieldBackedMapImpl::operator[](CelValue key) const {
-#ifdef GOOGLE_PROTOBUF_HAS_CEL_MAP_REFLECTION_FRIEND
+#ifdef XXX_GOOGLE_PROTOBUF_HAS_CEL_MAP_REFLECTION_FRIEND
+  static_assert(false);
+
   // Fast implementation.
   google::protobuf::MapKey inner_key;
   switch (key.type()) {
@@ -171,7 +173,7 @@ absl::optional<CelValue> FieldBackedMapImpl::operator[](CelValue key) const {
     return CreateErrorValue(arena_, status.message());
   }
   return result;
-#else   // GOOGLE_PROTOBUF_HAS_CEL_MAP_REFLECTION_FRIEND
+#else   // XXX_GOOGLE_PROTOBUF_HAS_CEL_MAP_REFLECTION_FRIEND
   // Slow implementation.
   CelValue result = CelValue::CreateNull();
   CelValue inner_key = CelValue::CreateNull();
@@ -228,7 +230,7 @@ absl::optional<CelValue> FieldBackedMapImpl::operator[](CelValue key) const {
   }
 
   return {};
-#endif  // GOOGLE_PROTOBUF_HAS_CEL_MAP_REFLECTION_FRIEND
+#endif  // XXX_GOOGLE_PROTOBUF_HAS_CEL_MAP_REFLECTION_FRIEND
 }
 
 }  // namespace runtime