Iron sword taking damage when hitting another player with it when pvp is set to false

What I expected to happen was...:
I did expect that when I hit other player (in server) with iron sword when server's pvp is set to false, sword shouldn't take damage at all.

What actually happened was...:
When I hit my friend with my iron sword, my sword took damage.

Steps to Reproduce:
1. Me and my friend were playing on our server (pvp false). Our client and server version were 13w07a.
2. I had iron sword with only three uses left.
3. I hit my friend with sword three times and it broke.

You should also notice:
I'm not any kind of expert, but I think this would be pretty important bugfix because usually, in non-pvp servers, people hits each other with sword, for fun.