diff --git a/Start/Server/Data/Services/BookmarkService.cs b/Start/Server/Data/Services/BookmarkService.cs
index e2e9b19..e6a716c 100644
--- a/Start/Server/Data/Services/BookmarkService.cs
+++ b/Start/Server/Data/Services/BookmarkService.cs
@@ -44,8 +44,11 @@ namespace Start.Server.Data.Services {
 		}
 
 		public async Task<Bookmark?> UpdateBookmark(string userId, Bookmark bookmark) {
-			Bookmark? existingBookmark = db.Bookmarks
-				.SingleOrDefault(b => b.BookmarkId == bookmark.BookmarkId);
+			Bookmark? existingBookmark = await db.Bookmarks
+				.SingleOrDefaultAsync(b => b.BookmarkId == bookmark.BookmarkId);
+
+			if (existingBookmark == null)
+				return null;
 
 			if (!BookmarkOwnershipTools.IsBookmarkOwner(this.db, userId, bookmark.BookmarkId))
 				return null;
@@ -55,6 +58,41 @@ namespace Start.Server.Data.Services {
 				.IsBookmarkGroupOwner(this.db, userId, bookmark.BookmarkGroupId))
 				return null;
 
+			if (bookmark.BookmarkGroupId != existingBookmark.BookmarkGroupId) {
+				// The bookmark was moved to a different group - shuffle sort order around
+				List<Bookmark>? oldGroupBookmarks = await db.Bookmarks
+					.Where(b => b.BookmarkGroupId == existingBookmark.BookmarkGroupId)
+					.Where(b => b.SortOrder > existingBookmark.SortOrder)
+					.ToListAsync();
+
+				oldGroupBookmarks.ForEach(b => b.SortOrder -= 1);
+
+				List<Bookmark>? newGroupBookmarks = await db.Bookmarks
+					.Where(b => b.BookmarkGroupId == bookmark.BookmarkGroupId)
+					.Where(b => b.SortOrder >= bookmark.SortOrder)
+					.ToListAsync();
+
+				newGroupBookmarks.ForEach(b => b.SortOrder += 1);
+			}
+			else if (bookmark.SortOrder != existingBookmark.SortOrder) {
+				// The bookmark has been moved within the same group
+
+				List<Bookmark>? groupBookmarks = await db.Bookmarks
+					.Where(b => b.BookmarkGroupId == bookmark.BookmarkGroupId)
+					.Where(b => b.BookmarkId != bookmark.BookmarkId)
+					.ToListAsync();
+
+				groupBookmarks
+					.Where(b => b.SortOrder > existingBookmark.SortOrder)
+					.ToList()
+					.ForEach(b => b.SortOrder -=1);
+
+				groupBookmarks
+					.Where(b => b.SortOrder > bookmark.SortOrder)
+					.ToList()
+					.ForEach(b => b.SortOrder += 1);
+			}
+
 			db.Entry(bookmark).State = EntityState.Modified;
 			await db.SaveChangesAsync();