Diamond Sword Will Not Break Blocks

A diamond sword will not break blocks.

I just randomly tried to dig up a gravel block with a diamond sword while going through a tunnel in creative mode.

The block wouldn't crack or break at all. I tried it on wood, cobble, and dirt additionally and got nothing. All other items do fine at breaking blocks.

1. Attempt to break a block with a diamond sword.
2. Block will not break