diff --git a/key/keypress_c.h b/key/keypress_c.h
index 2f225ed..3ed9b8a 100644
--- a/key/keypress_c.h
+++ b/key/keypress_c.h
@@ -19,6 +19,8 @@
 		Sleep(DEADBEEF_RANDRANGE(0, 1));
 	}
 #elif defined(USE_X11)
+	Display *XGetMainDisplay(void);
+	
 	void X_KEY_EVENT(Display *display, MMKeyCode key, bool is_press) {
 		XTestFakeKeyEvent(display, XKeysymToKeycode(display, key), is_press, CurrentTime); 
 		XSync(display, false);