diff --git a/lib/response.js b/lib/response.js
index 3ea3727..844c137 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -440,15 +440,14 @@ module.exports = {
 
   append: function(field, val){
     var prev = this.get(field);
-    var value = val;
+
     if (prev) {
-      // concat the new and prev vals
-      value = Array.isArray(prev) ? prev.concat(val)
-        : Array.isArray(val) ? [prev].concat(val)
-        : [prev, val];
+      val = Array.isArray(prev)
+        ? prev.concat(val)
+        : [prev].concat(val);
     }
 
-    return this.set(field, value);
+    return this.set(field, val);
   },
 
   /**