diff --git a/src/Fluxera.Entity/AggregateRoot.cs b/src/Fluxera.Entity/AggregateRoot.cs
index 4bbfaa9..684b961 100644
--- a/src/Fluxera.Entity/AggregateRoot.cs
+++ b/src/Fluxera.Entity/AggregateRoot.cs
@@ -11,7 +11,7 @@
 	[PublicAPI]
 	public abstract class AggregateRoot<TAggregateRoot, TKey> : Entity<TAggregateRoot, TKey>
 		where TAggregateRoot : AggregateRoot<TAggregateRoot, TKey>
-		where TKey : IComparable<TKey>, IEquatable<TKey>
+		where TKey : notnull, IComparable<TKey>, IEquatable<TKey>
 	{
 	}
 }
diff --git a/src/Fluxera.Entity/Entity.cs b/src/Fluxera.Entity/Entity.cs
index 4dcbae2..eda00a4 100644
--- a/src/Fluxera.Entity/Entity.cs
+++ b/src/Fluxera.Entity/Entity.cs
@@ -17,7 +17,7 @@
 	[PublicAPI]
 	public abstract class Entity<TEntity, TKey>
 		where TEntity : Entity<TEntity, TKey>
-		where TKey : IComparable<TKey>, IEquatable<TKey>
+		where TKey : notnull, IComparable<TKey>, IEquatable<TKey>
 	{
 		/// <summary>
 		///     To ensure hashcode uniqueness, a carefully selected random number multiplier
diff --git a/src/Fluxera.Entity/Fluxera.Entity.csproj b/src/Fluxera.Entity/Fluxera.Entity.csproj
index 3a1a767..75a737d 100644
--- a/src/Fluxera.Entity/Fluxera.Entity.csproj
+++ b/src/Fluxera.Entity/Fluxera.Entity.csproj
@@ -24,7 +24,7 @@
 	<ItemGroup>
 		<PackageReference Include="Fluxera.ComponentModel.Annotations" Version="6.0.9" />
 		<PackageReference Include="Fluxera.Guards" Version="6.0.22" />
-		<PackageReference Include="Fluxera.StronglyTypedId" Version="6.0.3" />
+		<PackageReference Include="Fluxera.StronglyTypedId" Version="6.0.4" />
 		<PackageReference Include="GitVersion.MsBuild" Version="5.10.3">
 		  <PrivateAssets>all</PrivateAssets>
 		  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>