Blocks not mining properly in creative whn holding a sword

When I try to destory an anvil in creative mode while holding any sword, it mines like I was in survival mode. However, if I try to destroy it while holding something else, it destroys normally.

EDIT: This applies to ALL blocks, not just anvils

EDIT: The blocks act like bedrock in survival when mined with a sword in creative mode. (they can't be destroyed)