diff --git a/Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift b/Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift
index 28f9c6629..6f181c926 100644
--- a/Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift
+++ b/Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift
@@ -319,9 +319,6 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
     private func didComplete(withAttachments attachments: [SignalAttachment]) {
         AssertIsOnMainThread()
 
-        // If we re-enter image picking, do so in batch mode.
-        isInBatchSelectMode = true
-
         for attachment in attachments {
             guard let assetId = attachment.assetId else {
                 owsFailDebug("Attachment is missing asset id.")
@@ -376,17 +373,6 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
         self.doneButton.isEnabled = false
     }
 
-    @objc
-    func didCancelSelect(_ sender: Any) {
-        endSelectMode()
-    }
-
-    func endSelectMode() {
-        isInBatchSelectMode = false
-
-        deselectAnySelected()
-    }
-
     func deselectAnySelected() {
         guard let collectionView = self.collectionView else {
             owsFailDebug("collectionView was unexpectedly nil")
@@ -520,6 +506,11 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
 
     override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
 
+        if !isInBatchSelectMode {
+            // Clear previous selection, if any.
+            selectedIds.removeAllObjects()
+        }
+
         let asset = photoCollectionContents.asset(at: indexPath.item)
         let assetId = asset.localIdentifier
         selectedIds.add(assetId)
@@ -577,6 +568,9 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
     }
 
     func attachmentApproval(_ attachmentApproval: AttachmentApprovalViewController, addMoreToAttachments attachments: [SignalAttachment]) {
+        // If we re-enter image picking via "add more" button, do so in batch mode.
+        isInBatchSelectMode = true
+
         navigationController?.popToViewController(self, animated: true)
     }
 
diff --git a/Signal/src/ViewControllers/PhotoLibrary/PhotoLibrary.swift b/Signal/src/ViewControllers/PhotoLibrary/PhotoLibrary.swift
index 86a45d86d..14d79b05f 100644
--- a/Signal/src/ViewControllers/PhotoLibrary/PhotoLibrary.swift
+++ b/Signal/src/ViewControllers/PhotoLibrary/PhotoLibrary.swift
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 import Foundation
@@ -48,12 +48,24 @@ class PhotoPickerAssetItem: PhotoGridItem {
 
     func asyncThumbnail(completion: @escaping (UIImage?) -> Void) -> UIImage? {
         var syncImageResult: UIImage?
+        var hasLoadedImage = false
 
         // Surprisingly, iOS will opportunistically run the completion block sync if the image is
-        // already available
+        // already available.
         photoCollectionContents.requestThumbnail(for: self.asset, thumbnailSize: photoMediaSize.thumbnailSize) { image, _ in
-            syncImageResult = image
-            completion(image)
+            DispatchMainThreadSafe({
+                syncImageResult = image
+
+                // Once we've _successfully_ completed (e.g. invoked the completion with
+                // a non-nil image), don't invoke the completion again with a nil argument.
+                if !hasLoadedImage || image != nil {
+                    completion(image)
+
+                    if image != nil {
+                        hasLoadedImage = true
+                    }
+                }
+            })
         }
         return syncImageResult
     }
@@ -294,7 +306,7 @@ class PhotoLibrary: NSObject, PHPhotoLibraryChangeObserver {
         let processPHAssetCollections: (PHFetchResult<PHAssetCollection>) -> Void = { (fetchResult) in
             // undocumented constant
 
-            fetchResult.enumerateObjects { (assetCollection, index, stop) in
+            fetchResult.enumerateObjects { (assetCollection, _, _) in
                 // We're already sorting albums by last-updated. "Recently Added" is mostly redundant
                 guard assetCollection.assetCollectionSubtype != .smartAlbumRecentlyAdded else {
                     return