diff --git a/src/calibre/gui2/layout.py b/src/calibre/gui2/layout.py
index e0a8325e0d..da79b9a44d 100644
--- a/src/calibre/gui2/layout.py
+++ b/src/calibre/gui2/layout.py
@@ -302,6 +302,7 @@ class ToolBar(QToolBar): # {{{
         text = _('%d books')%new_count
         a = self.choose_action
         a.setText(text)
+        a.setToolTip(_('Choose calibre library to work with') + '\n\n' + text)
 
     def resizeEvent(self, ev):
         QToolBar.resizeEvent(self, ev)