diff --git a/gdk/gdkconfig.h.meson b/gdk/gdkconfig.h.meson
index f832c043de..115c612d82 100644
--- a/gdk/gdkconfig.h.meson
+++ b/gdk/gdkconfig.h.meson
@@ -13,6 +13,7 @@ G_BEGIN_DECLS
 #mesondefine GDK_WINDOWING_X11
 #mesondefine GDK_WINDOWING_BROADWAY
 #mesondefine GDK_WINDOWING_WAYLAND
+#mesondefine GDK_WINDOWING_WIN32
 #mesondefine GDK_WINDOWING_MIR
 
 #mesondefine GDK_RENDERING_VULKAN