diff --git a/lib/class.js b/lib/class.js
index 99acddb..57bd48d 100644
--- a/lib/class.js
+++ b/lib/class.js
@@ -207,22 +207,39 @@ function prop_copy( props, dest, result_data )
     // because the length of the array remains the same after deleting elements)
     if ( abstract_regen )
     {
-        // copy the methods into a new array by pushing them onto it, to ensure
-        // the length property of the array will work properly
-        var methods_new = [];
-        for ( var i = 0, len = abstract_methods.length; i < len; i++ )
-        {
-            var method = abstract_methods[ i ];
-            if ( method === undefined )
-            {
-                continue;
-            }
+        result_data.abstractMethods = array_shrink( abstract_methods );
+    }
+}
 
-            methods_new.push( method );
+
+/**
+ * Shrinks an array, removing undefined elements
+ *
+ * Pushes all items onto a new array, removing undefined elements. This ensures
+ * that the length of the array represents correctly the number of elements in
+ * the array.
+ *
+ * @param  {Array}  items  array to shrink
+ *
+ * @return  {Array}  shrunken array
+ */
+function array_shrink( items )
+{
+    // copy the methods into a new array by pushing them onto it, to ensure
+    // the length property of the array will work properly
+    var arr_new = [];
+    for ( var i = 0, len = items.length; i < len; i++ )
+    {
+        var item = items[ i ];
+        if ( item === undefined )
+        {
+            continue;
         }
 
-        result_data.abstractMethods = methods_new;
+        arr_new.push( item );
     }
+
+    return arr_new;
 }