diff --git a/Signal/src/ViewControllers/MediaGalleryViewController.swift b/Signal/src/ViewControllers/MediaGalleryViewController.swift
index e33d8fdeb..6a63a548e 100644
--- a/Signal/src/ViewControllers/MediaGalleryViewController.swift
+++ b/Signal/src/ViewControllers/MediaGalleryViewController.swift
@@ -35,7 +35,7 @@ public struct MediaGalleryItem: Equatable, Hashable {
 
     var thumbnailImage: UIImage {
         guard let image = attachmentStream.thumbnailImage() else {
-//            owsFail("\(logTag) in \(#function) unexpectedly unable to build attachment thumbnail")
+            owsFail("\(logTag) in \(#function) unexpectedly unable to build attachment thumbnail")
             return UIImage()
         }
 
diff --git a/Signal/src/ViewControllers/MediaTileViewController.swift b/Signal/src/ViewControllers/MediaTileViewController.swift
index a76c91c01..7cfc9f1ee 100644
--- a/Signal/src/ViewControllers/MediaTileViewController.swift
+++ b/Signal/src/ViewControllers/MediaTileViewController.swift
@@ -8,7 +8,7 @@ public protocol MediaTileViewControllerDelegate: class {
     func mediaTileViewController(_ viewController: MediaTileViewController, didTapView tappedView: UIView, mediaGalleryItem: MediaGalleryItem)
 }
 
-public class MediaTileViewController: UICollectionViewController, MediaGalleryDataSourceDelegate {
+public class MediaTileViewController: UICollectionViewController, MediaGalleryDataSourceDelegate, UICollectionViewDelegateFlowLayout {
 
     private weak var mediaGalleryDataSource: MediaGalleryDataSource?