diff --git a/themes/base/jquery.ui.progressbar.css b/themes/base/jquery.ui.progressbar.css
index 38364fafa..79d786fa7 100644
--- a/themes/base/jquery.ui.progressbar.css
+++ b/themes/base/jquery.ui.progressbar.css
@@ -7,5 +7,5 @@
  *
  * http://docs.jquery.com/UI/Progressbar#theming
  */
-.ui-progressbar { height:2em; text-align: left; }
+.ui-progressbar { height:2em; text-align: left; overflow: hidden; }
 .ui-progressbar .ui-progressbar-value {margin: -1px; height:100%; }
\ No newline at end of file