diff --git a/lib/renderer.js b/lib/renderer.js
index b1000d5..7038c4d 100644
--- a/lib/renderer.js
+++ b/lib/renderer.js
@@ -36,7 +36,7 @@ default_rules.fence = function (tokens, idx, options, env, slf) {
 
   if (info) {
     langName = info.split(/\s+/g)[0];
-    token.attrPush([ 'class', options.langPrefix + langName ]);
+    token.attrJoin('class', options.langPrefix + langName);
   }
 
   if (options.highlight) {