NSInteger set to 0 but returns nil

I have an NSInteger in my class like so

In @interface:

NSInteger currentRow;    

@property (assign) NSInteger currentRow;

In @implementation:

@synthesize currentRow;

Doing [self setCurrentRow:0] seems to work fine, but using [self currentRow] just returns null for some reason, not sure why. When using breakpoints I can see that the value for currentRow is 0 so it has set fine, but I can't get the value back.