Yesterday I made a stupid mistake. I wanted to get rid of a received dust transaction of 547 sat and tried to send it to a another address with a very low fee of only 336 sat.
For future reference, here is a guide showing how to dump the 547 satoshis if you use Electrum:
https://gist.github.com/ncstdc/90fe6209a0b3ae815a6eaa2aef53524c