diff --git a/lib/6to5/transform.js b/lib/6to5/transform.js
index ec492bbb77..6c8867fc52 100644
--- a/lib/6to5/transform.js
+++ b/lib/6to5/transform.js
@@ -57,9 +57,12 @@ transform.test = function (task, assert) {
     var consumer = new sourceMap.SourceMapConsumer(result.map);
 
     _.each(task.sourceMappings, function (mapping, i) {
-      var pos = consumer.originalPositionFor(mapping.generated);
-      var msg = "source mapping " + i + " - generated: " + mapping.generated.line + ":" + mapping.generated.column;
-      assert.equal(pos.line + ":" + pos.column, mapping.original.line + ":" + mapping.original.column, msg);
+      var generated = mapping.generated;
+      var original  = mapping.original;
+
+      var pos = consumer.originalPositionFor(generated);
+      var msg = "source mapping " + i + " - generated: " + generated.line + ":" + generated.column;
+      assert.equal(pos.line + ":" + pos.column, original.line + ":" + original.column, msg);
     });
   }
 };