diff --git a/IPython/html/static/notebook/less/tooltip.less b/IPython/html/static/notebook/less/tooltip.less
index ba49433..9f6d2fa 100644
--- a/IPython/html/static/notebook/less/tooltip.less
+++ b/IPython/html/static/notebook/less/tooltip.less
@@ -117,7 +117,7 @@
     };
     position: absolute;
 
-	z-index: 2;
+	z-index: 1000;
 	
 	.tooltiptext {
 		pre {