diff --git a/.speakeasy/gen.yaml b/.speakeasy/gen.yaml
index 30b65e5..50ea340 100644
--- a/.speakeasy/gen.yaml
+++ b/.speakeasy/gen.yaml
@@ -59,6 +59,7 @@ python:
   flattenGlobalSecurity: true
   flattenRequests: true
   flatteningOrder: parameters-first
+  forwardCompatibleUnionsByDefault: "tagged-only"
   imports:
     option: openapi
     paths: