diff --git a/book/tex4ebook.cfg b/book/tex4ebook.cfg
index 35066f6..2a43f4d 100644
--- a/book/tex4ebook.cfg
+++ b/book/tex4ebook.cfg
@@ -33,4 +33,13 @@
 }
 \makeatother
 
+% Warnig from Michal: Note that once you get the updated TeX Live with a new
+% `chemfig.4ht` file, you can remove this from the config file:
+%
+%```latex \pend:def\schemestart{\Picture+{}}
+%\append:def\CF_schemestop{\EndPicture} ```
+%
+%You could get an error otherwise, as there would be nested `\Picture+{}` and
+%`\EndPicture` commands.
+
 \EndPreamble