diff --git a/xkb/xkb.c b/xkb/xkb.c
index 001e5928f..582749fc1 100644
--- a/xkb/xkb.c
+++ b/xkb/xkb.c
@@ -2463,7 +2463,8 @@ _XkbSetMapCheckLength(xkbSetMapReq *req)
     if (len == req_len)
         return Success;
 bad:
-    ErrorF("[xkb] BOGUS LENGTH in SetMap: expected %zd got %zd\n", len, req_len);
+    ErrorF("[xkb] BOGUS LENGTH in SetMap: expected %lu got %lu\n",
+        (unsigned long int)len, (unsigned long int)req_len);
     return BadLength;
 }