--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -7847,16 +7847,17 @@ var gPageActionButton = {
       if (!name) {
         return document.createElement("toolbarseparator");
       }
       let item = document.createElement("toolbarbutton");
       item.classList.add("page-action-sendToDevice-device", "subviewbutton");
       if (clientId) {
         item.classList.add("subviewbutton-iconic");
       }
+      item.setAttribute("tooltiptext", name);
       return item;
     });
 
     if (gSync.remoteClients.length) {
       body.setAttribute("hasdevices", "true");
     } else {
       body.removeAttribute("hasdevices");
     }