Strange warnings from htmlize.el

[Angelo Graziosi]

With the last Emacs master build (20240731_183641) I get a lot of 
warnings like this:

Warning (emacs): Cannot fontify source block (htmlize.el >= 1.34 required)


when I export an old ORG document in HTML (C-c C-e h h).

Until some time ago, I had  exported the same document and many more in 
the same manner and never seen those warnings (just Emacs master and ORG 
versions changed).

What happened?

Ciao,
  Angelo.