 extension ExploreViewController {
     override func collectionView(_ collectionView: UICollectionView, estimatedHeightForItemAt indexPath: IndexPath, forColumnWidth columnWidth: CGFloat) -> WMFLayoutEstimate {
         var estimate = WMFLayoutEstimate(precalculated: false, height: 100)
-        guard let placeholderCell = layoutManager.placeholder(forCellWithReuseIdentifier: cellReuseIdentifier) as? ExploreCardCollectionViewCell else {
+        guard let placeholderCell = layoutManager.placeholder(forCellWithReuseIdentifier: ExploreCardCollectionViewCell.identifier) as? ExploreCardCollectionViewCell else {
             return estimate
         }
         placeholderCell.prepareForReuse()

    
    override func collectionView(_ collectionView: UICollectionView, estimatedHeightForHeaderInSection section: Int, forColumnWidth columnWidth: CGFloat) -> WMFLayoutEstimate {
        var estimate = WMFLayoutEstimate(precalculated: false, height: 100)
        guard let header = layoutManager.placeholder(forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: headerReuseIdentifier) as? ExploreHeaderCollectionReusableView else {
            return estimate
        }
        header.prepareForReuse()

        layoutCache.reset()
    }
    
    // MARK - UICollectionViewDataSource
    
    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        guard let sections = fetchedResultsController.sections, sections.count > section else {
            return 0
