Sleeping in bed underground and saw sky

While under ground at layer 20 I mined out a space of 5 length by 5 width by 2 high and placed a bed. It was 1 block away from the west wall and 1 block away from the north wall with the foot of the bed facing south. When it was night, I right clicked on the bed from the foot of the bed looking north and it let me go to sleep. However instead of viewing the bottom side of the blocks of layer 23, the view presented me a shot of the sky littered with stars. I was able to replicate this after setting the time back to night and capturing some screen shots.

I expected to see the bottom side of the blocks of layer 23.

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