mumamo-fontify-region fails

Getting this in my *messages* most of the time when I open .html or .php files:

MU:mumamo-fontify-region: fun-var-sym=mumamo-eval-in-javascript-mode, use-major-entry=(javascript-mode (mumamo-eval-in-javascript-mode mumamo-def-eval-in-javascript-mode mumamo-kw-eval-in-javascript-mode))
** In buffer berend.html
  backtrace()
  mumamo-display-error(mumamo-fontify-region "%s" "fun-var-sym=mumamo-eval-in-javascript-mode, use-major-entry=(javascript-mode (mumamo-eval-in-javascript-mode mumamo-def-eval-in-javascript-mode mumamo-kw-eval-in-javascript-mode))")
  byte-code("\301\302\303\304!#\207" [err mumamo-display-error mumamo-fontify-region "%s" error-message-string] 5)
  mumamo-fontify-region(4042 4627 nil)
  font-lock-fontify-region(4042 4627)
  run-hook-with-args(font-lock-fontify-region 4042 4627)
  byte-code("\302\303 #\207" [start next run-hook-with-args jit-lock-functions] 4)
  jit-lock-fontify-now(4042 4542)
  jit-lock-function(4042)
  mumamo-jit-lock-function(4042)

mumamo-fontify-region: fun-var-sym=mumamo-eval-in-javascript-mode, use-major-entry=(javascript-mode (mumamo-eval-in-javascript-mode mumamo-def-eval-in-javascript-mode mumamo-kw-eval-in-javascript-mode))

No clue what else to report or how to debug.