msg notification doesn't go even after reading it

I have a galaxy core. The problem is minor but a problem is a problem. As you all know The msg icon in the home screen will show the no. of unread msgs if any. Now this number at the corner of the msg. icon should get erased after i read the msgs in the inbox. But its not. It only goes after i restart the phone. I've installed all the updates but the problem continues.

Thanks in advance.