1 files changed, 1 insertions, 2 deletions
diff --git a/src/SMAPI/Framework/StateTracking/FieldWatchers/NetDictionaryWatcher.cs b/src/SMAPI/Framework/StateTracking/FieldWatchers/NetDictionaryWatcher.cs
index 0d7f2ad2..f55e4cea 100644
--- a/src/SMAPI/Framework/StateTracking/FieldWatchers/NetDictionaryWatcher.cs
+++ b/src/SMAPI/Framework/StateTracking/FieldWatchers/NetDictionaryWatcher.cs
@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Collections.Generic;
 using Netcode;
 
@@ -12,6 +10,7 @@ namespace StardewModdingAPI.Framework.StateTracking.FieldWatchers
     /// <typeparam name="TSerialDict">The serializable dictionary type that can store the keys and values.</typeparam>
     /// <typeparam name="TSelf">The net field instance type.</typeparam>
     internal class NetDictionaryWatcher<TKey, TValue, TField, TSerialDict, TSelf> : BaseDisposableWatcher, IDictionaryWatcher<TKey, TValue>
+        where TKey : notnull
         where TField : class, INetObject<INetSerializable>, new()
         where TSerialDict : IDictionary<TKey, TValue>, new()
         where TSelf : NetDictionary<TKey, TValue, TField, TSerialDict, TSelf>