Seemingly incorrect mocking behaviour using OCMock

I'm doing something like this in my test

- (void)testSomething {
    __block BOOL isActive = NO;
    void (^doSomething)(void) = ^void(void) {
        isActive = YES;
        .....
    }

    [[someMock stub] andDo:^(NSInvocation *invocation) {
        NSValue *returnValue = 
            [NSValue valueWithBytes:&isRegistrationClientActive
                           objCType:@encode(BOOL)];
        [invocation setReturnValue:&returnValue];
     }] isSomeMockActive];

     [self.someObject doSomethingWithHandler:doSomething];

     /// === verify ===
}

What I've observed is when isSomeMockActive is hit my isActive is correct NO and then YES but invariably what is being returned by isSomeMockActive is always NO.

PS: I've tried using [self.mock stub] andReturnValue:...] and that seems to be having the same issue.

Is there anything wrong I'm doing?