No transparency in 'background-color' after css compression. What is the reason?

Question

css

After gulp compression, the background-color is empty. Why??

customs__button:hover {
  -webkit-transition: .2s;
  -o-transition: .2s;
  transition: .2s;
  background-color: #00000094;
  color: #ff9b51;
  -webkit-box-shadow: 0 0 0 2px #ff9b51, 0 0 0 2px #ffffff;
          box-shadow: 0 0 0 2px #ff9b51, 0 0 0 2px #ffffff;
}