diff --git a/lib/x11/corereqs.js b/lib/x11/corereqs.js
index 689eceb..ab3f3f8 100644
--- a/lib/x11/corereqs.js
+++ b/lib/x11/corereqs.js
@@ -206,7 +206,7 @@ module.exports = {
 
    PolyFillRectangle: [
       function(drawable, gc, rects) { // x1, y1, w1, h1, x2, y2, w2, h2...
-          var format = 'CxSL';
+          var format = 'CxSLL';
           var numrects4bytes = rects.len*2;
           var args = [60, 3+numrects4bytes, drawable, gc];
           for (var i=0; i < rects.length; ++i)