diff --git a/gen/schema_gen_sum.go b/gen/schema_gen_sum.go
index 083952c26..a5dbaa8fd 100644
--- a/gen/schema_gen_sum.go
+++ b/gen/schema_gen_sum.go
@@ -465,10 +465,9 @@ func (g *schemaGen) allOf(name string, schema *jsonschema.Schema) (*ir.Type, err
 		return nil, err
 	}
 
-	// Do not modify reference fields, as they may still refer to the original schema.
-	if mergedSchema.Ref.IsZero() {
-		mergedSchema.Ref = schema.Ref
-	}
+	// The reference field must not change
+	mergedSchema.Ref = schema.Ref
+
 	return g.generate(name, mergedSchema, false)
 }