Simple if statement is failing

I have this code where the value of shopOpenHour is @"0800" :

if([[shopOpenHour substringFromIndex: 2] isEqualToString: @"00"])
    minute = 0;
else
    minute = 30;

The if statement fails and hits the else statement instead. I have tried using braces around the if and else statements, but makes no difference.

What's wrong with the if statement?