diff --git a/render.js b/render.js
index 1c0d51a..215a44e 100644
--- a/render.js
+++ b/render.js
@@ -711,8 +711,9 @@
     }
     return 0;
   }
-  grid.data.sort(comparator);
-  return grid;
+  var outdata = grid.data.concat();
+  outdata.sort(comparator);
+  return { headers: grid.headers, data: outdata, types: grid.types };
 }