--- a/devtools/client/netmonitor/netmonitor.xul
+++ b/devtools/client/netmonitor/netmonitor.xul
@@ -295,17 +295,17 @@
                       standalone="true"
                       label="&netmonitorUI.reloadNotice2;"/>
               <label value="&netmonitorUI.reloadNotice3;"/>
             </hbox>
             <hbox id="notice-perf-message" align="center">
               <label value="&netmonitorUI.perfNotice1;"/>
               <button id="requests-menu-perf-notice-button"
                       standalone="true"
-                      label="&netmonitorUI.perfNotice3;"
+                      tooltiptext="&netmonitorUI.perfNotice3;"
                       class="devtools-toolbarbutton"/>
               <label value="&netmonitorUI.perfNotice2;"/>
             </hbox>
           </vbox>
 
           <vbox id="requests-menu-contents" flex="1" context="network-request-popup">
             <hbox id="requests-menu-item-template" hidden="true">
               <hbox class="requests-menu-subitem requests-menu-status"