My inventory says that I'm holding a diamond pick axe but I'm the texture in my hand is as a diamond axe

My inventory says that I'm holding a diamond pick axe but I'm the texture in my hand is as a diamond axe

What I expected to happen was...:
I mine happily in my mine while using my diamond pickaxe

What actually happened was...:
My inventory says that I'm holding a diamond pick axe but I'm the texture in my hand is as a diamond axe