diff --git a/widget/gtk/mozwayland/mozwayland.c b/widget/gtk/mozwayland/mozwayland.c

--- a/widget/gtk/mozwayland/mozwayland.c

+++ b/widget/gtk/mozwayland/mozwayland.c

@@ -200,3 +200,10 @@

 MOZ_EXPORT void wl_list_insert_list(struct wl_list* list,

                                     struct wl_list* other) {}

+

+MOZ_EXPORT struct wl_proxy* wl_proxy_marshal_flags(

+    struct wl_proxy* proxy, uint32_t opcode,

+    const struct wl_interface* interface, uint32_t version, uint32_t flags,

+    ...) {

+  return NULL;

+}