diff --git a/backend/server.go b/backend/server.go
index 4369d2f..0fc5556 100644
--- a/backend/server.go
+++ b/backend/server.go
@@ -363,6 +363,7 @@
 			msg := fmt.Sprintf("%s:1:1: error: %s", fidl, err)
 			return response{Ok: false, Content: msg}, nil
 		}
+		args = append(args, "--experimental", "old_syntax_only")
 		run, err := s.fidlc.run(ctx, append(args, fileArgs...)...)
 		if err != nil {
 			return response{}, err