diff --git a/public/static/pdf/web/viewer.html b/public/static/pdf/web/viewer.html
index 7960eef41..e9673f3e2 100644
--- a/public/static/pdf/web/viewer.html
+++ b/public/static/pdf/web/viewer.html
@@ -345,9 +345,9 @@ See https://github.com/adobe-type-tools/cmap-resources
           <div id="toolbarContainer">
             <div id="toolbarViewer">
               <div id="toolbarViewerLeft">
-<!--                <button id="sidebarToggle" class="toolbarButton" title="Toggle Sidebar" tabindex="11" data-l10n-id="toggle_sidebar">-->
-                  <!--                  <span data-l10n-id="toggle_sidebar_label">Toggle Sidebar</span>-->
-                  <!--                </button>-->
+                <button id="sidebarToggle" class="toolbarButton" style="display: none" title="Toggle Sidebar" tabindex="11" data-l10n-id="toggle_sidebar">
+                  <span data-l10n-id="toggle_sidebar_label">Toggle Sidebar</span>
+                </button>
                 <div class="toolbarButtonSpacer"></div>
                 <button id="viewFind" class="toolbarButton" title="Find in Document" tabindex="12" data-l10n-id="findbar">
                   <span data-l10n-id="findbar_label">Find</span>