diff --git a/xfixes/select.c b/xfixes/select.c
index c088ed3de..e964d588c 100644
--- a/xfixes/select.c
+++ b/xfixes/select.c
@@ -201,6 +201,7 @@ SProcXFixesSelectSelectionInput(ClientPtr client)
 {
     REQUEST(xXFixesSelectSelectionInputReq);
 
+    REQUEST_SIZE_MATCH(xXFixesSelectSelectionInputReq);
     swaps(&stuff->length);
     swapl(&stuff->window);
     swapl(&stuff->selection);