Impulse command block not performing command after the command block behind it has performed its command

1. Have a repeating command block that keeps checking for a /testfor
2. Have a command block in front that does a desired action upon success from the previous command block
3. The Impulse command block doesn't do its action

HOWEVER;
If the command block is a Chain command block, it works.
If the command block is powered by a redstone comparator it works.