diff --git a/dix/getevents.c b/dix/getevents.c
index 1671a2411a..88299b04e7 100644
--- a/dix/getevents.c
+++ b/dix/getevents.c
@@ -486,6 +486,9 @@ GetMaximumEventsNum(void) {
 #endif
         ret *= 2;
 
+    /* One possible DeviceClassesChangedEvent */
+    ret++;
+
     return ret;
 }