UICollectionViewController Programmatically crashing with non-nil layout parameter error

I am creating a UICollectionViewController programmatically. No, I don't want to use IB and Storyboards like every tutorial out there. I just want to use plain code.

Here is what I have in my viewDidLoad:

// UICollectionView
    UICollectionViewFlowLayout *aFlowLayout = [[UICollectionViewFlowLayout alloc] init];
    [aFlowLayout setItemSize:CGSizeMake(200, 140)];
    [aFlowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
    self.collectionView = [[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:aFlowLayout];
    [self.collectionView setDelegate:self];
    [self.collectionView setDataSource:self];
    self.collectionView.backgroundColor = [UIColor clearColor];
    [self.collectionView setAutoresizingMask:UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleWidth];
    [self.collectionView registerClass:[PUCImageGridCell class] forCellWithReuseIdentifier:CollectionViewCellIdentifier];

I have implemented the required delegate methods and I still get this error:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter'