diff --git a/lib/model/source/album.dart b/lib/model/source/album.dart
index 88aa723d6..eedeea81c 100644
--- a/lib/model/source/album.dart
+++ b/lib/model/source/album.dart
@@ -178,17 +178,17 @@ mixin AlbumMixin on SourceBase {
       return volume.getDescription(context);
     }
 
-    String unique(String dirPath, Set<String?> others) {
+    String unique(String dirPath, Set<String> others) {
       final parts = pContext.split(dirPath);
       for (var i = parts.length - 1; i > 0; i--) {
         final name = pContext.joinAll(['', ...parts.skip(i)]);
         final testName = '$separator$name';
-        if (others.every((item) => !item!.endsWith(testName))) return name;
+        if (others.every((item) => !item.endsWith(testName))) return name;
       }
       return dirPath;
     }
 
-    final otherAlbumsOnDevice = _directories.where((item) => item != dirPath).toSet();
+    final otherAlbumsOnDevice = _directories.whereNotNull().where((item) => item != dirPath).toSet();
     final uniqueNameInDevice = unique(dirPath, otherAlbumsOnDevice);
     if (uniqueNameInDevice.length <= relativeDir.length) {
       return uniqueNameInDevice;