Pins don't go HIGH anymore

PWM 255 as well as digitalWrite(PIN,HIGH) isn't HIGH any more.
Now there is a PWM spike on the signal. Seems that PWM 254 is the maximum HIGH level now.
LOW Level works (as mentioned within the README.md "True zero level, i.e. off == off").
HIGH Level is not mentioned :-)
I really appreciate the  purpose of this library.