diff --git a/dlls/winex11.drv/event.c b/dlls/winex11.drv/event.c
index 542fce892eb..956e4f1c884 100644
--- a/dlls/winex11.drv/event.c
+++ b/dlls/winex11.drv/event.c
@@ -323,7 +323,7 @@ static inline void call_event_handler( Display *display, XEvent *event )
 /***********************************************************************
  *           process_events
  */
-static int process_events( Display *display, Bool (*filter)(), ULONG_PTR arg )
+static int process_events( Display *display, Bool (*filter)(Display*, XEvent*,XPointer), ULONG_PTR arg )
 {
     XEvent event, prev_event;
     int count = 0;