diff --git a/ui.h b/ui.h
index b5fb9a27..429c3780 100644
--- a/ui.h
+++ b/ui.h
@@ -80,6 +80,7 @@ struct uiControl {
 	uint32_t Signature;
 	uint32_t OSSignature;
 	uint32_t TypeSignature;
+	void *user;
 	void (*Destroy)(uiControl *);
 	uintptr_t (*Handle)(uiControl *);
 	uiControl *(*Parent)(uiControl *);