diff --git a/dawn.json b/dawn.json
index b849ff8..434ad14 100644
--- a/dawn.json
+++ b/dawn.json
@@ -595,7 +595,7 @@
                 "name": "create swap chain",
                 "returns": "swap chain",
                 "args": [
-                    {"name": "surface", "type": "surface"},
+                    {"name": "surface", "type": "surface", "optional": "true"},
                     {"name": "descriptor", "type": "swap chain descriptor", "annotation": "const*"}
                 ]
             },