diff --git a/IPython/frontend/html/notebook/static/css/notebook.css b/IPython/frontend/html/notebook/static/css/notebook.css
index c085244..a9f2862 100644
--- a/IPython/frontend/html/notebook/static/css/notebook.css
+++ b/IPython/frontend/html/notebook/static/css/notebook.css
@@ -278,7 +278,7 @@ div.text_cell_render {
 .completions {
     position: absolute;
     z-index: 10;
-    overflow: auto;
+    overflow: hidden;
     border: 1px solid grey;
 }
 
@@ -288,6 +288,7 @@ div.text_cell_render {
     border: none;
     padding: 0px;
     margin: 0px;
+    overflow: auto;
     font-family: monospace;
 }