diff --git a/lib/x11/corereqs.js b/lib/x11/corereqs.js
index 79946ea..e2fcee4 100644
--- a/lib/x11/corereqs.js
+++ b/lib/x11/corereqs.js
@@ -164,7 +164,7 @@ module.exports = {
            // TODO: maybe it's better just to scan all 32 bits anstead of sorting parameters we are actually have?
            for (m in masksList)
            {
-              valueName = valueMaskName['CreateWindow'][masksList[m]];
+              var valueName = valueMaskName['CreateWindow'][masksList[m]];
               args.push( values[valueName] );
            }
            return [format, args];