diff --git a/text_resize.js b/text_resize.js
index d3001fe..2e7e032 100644
--- a/text_resize.js
+++ b/text_resize.js
@@ -94,11 +94,11 @@
           return false;
         }
         else if (reset_size_original == true) {
-          element_to_resize.css('font-size', null);
+          element_to_resize.css('font-size', '');
           if (text_resize_line_height_allow) { element_to_resize.css('line-height', null); }
           return false;
         }
       });
     }
   };
-})(jQuery);
\ No newline at end of file
+})(jQuery);