/fill lighting glitch

Take a look at these photos. I wanted to make a quick dark arena type thing with the /fill command. But then I realized that light was still coming through the walls and ceiling of the bedrock I placed with the /fill command. I also tried it with other blocks and it still did not work.

There used to be light diamonds like the ones in the picture everywhere on the ceiling but I filled them in with dirt I hand placed and was able to get rid of most of them, but I couldn't get light from getting through the walls. The second picture shows what my land looks like, it's still light even though it is within I giant bedrock box with no holes.

I've made giant ceilings before in past versions without /fill and it made the land very dark below it, please fix, this has made me really frustrated!

Thanks