Emacs 23.3 stops font-lock when have long face name

[wsnyder@wsnyder.org (Wilson Snyder)]

I'm trying to fix a font-lock issue with long face names
reported against Emacs 23.3, which I've confirmed is fixed
in Emacs 25.

There's a keyword list:

  (setq verilog-font-lock-keywords
     ....
     (cons (concat "\\<\\(" verilog-font-grouping-keywords "\\)\\>")
	   'verilog-font-lock-fixme-face)

this works correctly.  Changing the face name used to 

           'verilog-font-lock-fixmefixmefixmefixmefixmefixmefixme-face)

which has an identical face definition as the shorter name,
makes the fontification break - font-lock simply stops
highlighting using this face half way through the smallish
buffer, but continues using other (shorter) face names.

This is not affected by font-lock-maximum-size.

Can anyone please suggest what version this was fixed and
suggest a workaround for the older Emacsen?

I would prefer not to rename the long face's name (really
it's verilog-font-grouping-keywords-face) since that name
has been stable for several versions of Emacs and may be in
user's customizations.

Thanks