diff --git a/interop/proto/mls_client.proto b/interop/proto/mls_client.proto
index 09c426c..240b98a 100644
--- a/interop/proto/mls_client.proto
+++ b/interop/proto/mls_client.proto
@@ -324,8 +324,8 @@ message CreateBranchRequest {
   bytes group_id = 2;
   repeated Extension extensions = 3;
   repeated bytes key_packages = 4;
-  bool forcePath = 5;
-  bool externalTree = 6;
+  bool force_path = 5;
+  bool external_tree = 6;
 }
 
 message CreateBranchResponse {