diff --git a/src/pyj/read_book/footnotes.pyj b/src/pyj/read_book/footnotes.pyj
index 830980731e..ac7d508db4 100644
--- a/src/pyj/read_book/footnotes.pyj
+++ b/src/pyj/read_book/footnotes.pyj
@@ -224,6 +224,7 @@ class PopupIframeBoss:
         show_footnote(self.frag, known_anchors)
 
     def content_loaded(self):
+        document.body.classList.add('calibre-footnote-container')
         if not self.comm.encrypted_communications:
             window.setTimeout(self.content_loaded, 2)
             return