--- a/devtools/client/netmonitor/netmonitor.css
+++ b/devtools/client/netmonitor/netmonitor.css
@@ -2,16 +2,24 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #toolbar-labels {
   overflow: hidden;
 }
 
+/**
+ * Collapsed details pane needs to be truly hidden to prevent both accessibility
+ * tools and keyboard from accessing its contents.
+ */
+#details-pane.pane-collapsed {
+  visibility: hidden;
+}
+
 #details-pane-toggle[disabled] {
   display: none;
 }
 
 #custom-pane {
   overflow: auto;
 }
 
@@ -31,14 +39,13 @@
   /* workaround for textbox not supporting the @crop attribute */
   text-overflow: ellipsis;
 }
 
 /* Responsive sidebar */
 @media (max-width: 700px) {
   #toolbar-spacer,
   #details-pane-toggle,
-  #details-pane.pane-collapsed,
   .requests-menu-waterfall,
   #requests-menu-network-summary-button > .toolbarbutton-text {
     display: none;
   }
 }