diff --git a/IPython/html/static/base/less/flexbox.less b/IPython/html/static/base/less/flexbox.less
index 99e4cbe..60874fc 100644
--- a/IPython/html/static/base/less/flexbox.less
+++ b/IPython/html/static/base/less/flexbox.less
@@ -98,6 +98,7 @@ Browsers not listed, including Safari, are supported via the styling under the
     
     /* Modern browsers */
     flex: none;
+    width: auto;
 }
 
 .box-flex1 {