diff --git a/DiscordDelete/ScanOptions.cs b/DiscordDelete/ScanOptions.cs
index a330cbd..124d295 100644
--- a/DiscordDelete/ScanOptions.cs
+++ b/DiscordDelete/ScanOptions.cs
@@ -9,13 +9,13 @@ namespace DiscordDelete
     [Verb("scan", HelpText = "Delete all saved messages.")]
     public class ScanOptions
     {
-        [Option('g', "guild")]
+        [Option('g', "guild", ResourceType = typeof(string), Default = null)]
         public string? GuildId { get; set; }
 
-        [Option('c', "channel")]
+        [Option('c', "channel", ResourceType = typeof(string))]
         public string? ChannelId { get; set; }
 
-        [Option('a', "author", Required = true)]
+        [Option('a', "author", Required = true, ResourceType = typeof(string))]
         public string? Author { get; set; }
     }
 }