diff --git a/dix/inpututils.c b/dix/inpututils.c
index 60f9fa0a8..5e2ab87f9 100644
--- a/dix/inpututils.c
+++ b/dix/inpututils.c
@@ -626,7 +626,7 @@ void verify_internal_event(const InternalEvent *ev)
     if (ev && ev->any.header != ET_Internal)
     {
         int i;
-        unsigned char *data = (unsigned char*)ev;
+        const unsigned char *data = (const unsigned char*)ev;
 
         ErrorF("dix: invalid event type %d\n", ev->any.header);