Bug [Editor] Broken Importer selector

I'm trying to create a custom importer for package manifest files, which have .json extension.
This is my code:

Code (CSharp):

1. [ScriptedImporter(1, null, new string[] { "json" })]
2. public class PackageManifestImporter : ScriptedImporter
3. {
4.     private static Texture2D manifestIcon;
5.  
6.     public override void OnImportAsset(AssetImportContext ctx)
7.     {
8.         var manifestJson = File.ReadAllText(ctx.assetPath);
9.         var manifestAsset = ScriptableObject.CreateInstance<PackageManifestAsset>();
10.         JsonUtility.FromJsonOverwrite(manifestJson, manifestAsset);
11.         EditorUtility.SetDirty(this);
12.  
13.         if (manifestIcon == null)
14.             manifestIcon = EditorGUIUtility.IconContent("d_TextScriptImporter Icon").image as Texture2D;
15.         ctx.AddObjectToAsset(ctx.assetPath, manifestAsset, manifestIcon);
16.         ctx.SetMainObject(manifestAsset);
17.     }
18. }

My importer is shown in the Inspector in the top selection dropdown but it just doesn't work: when I select a different entry nothing happens, the first one is always selected (this happens by default, even if I don't create the third entry)

 

I just tried with different extensions ("txt" and "png") and the same problem occurs: the importer is recognized but it is not selectable

 

Ok this was a totally stupid problem.
I changed the name of the importer and the selector started working. I used the same name as a built-in importer and the editor didn't like that. Please Unity, spawn a warning or something!