@eiten Ran into the same error but of course the community is always at hand, ready to help! Great! I'm using MySensors 2.3.2 release version. Downgrading the ESP8266 board library to 2.7.4 as suggested by @OldSurferDude did the trick. I'm still clinging to MySensors. So simple and inexpensive to use! All sensors and other stuff connects over three MQTT GW in three locations back to my Home Assistant. PS: Get well soon! Regards, Gunnar