diff --git a/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs b/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs
index 4c9ca2ff..960caf96 100644
--- a/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs
+++ b/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs
@@ -16,15 +16,15 @@ namespace StardewModdingAPI.Toolkit.Framework.UpdateData
         public ModSiteKey Site { get; }
 
         /// <summary>The mod ID within the repository.</summary>
-#if NET5_0_OR_GREATER
-        [MemberNotNullWhen(true, nameof(LooksValid))]
-#endif
         public string? ID { get; }
 
         /// <summary>If specified, a substring in download names/descriptions to match.</summary>
         public string? Subkey { get; }
 
         /// <summary>Whether the update key seems to be valid.</summary>
+#if NET5_0_OR_GREATER
+        [MemberNotNullWhen(true, nameof(UpdateKey.ID))]
+#endif
         public bool LooksValid { get; }