diff --git a/src/EFCore/Infrastructure/ModelValidator.cs b/src/EFCore/Infrastructure/ModelValidator.cs
index 4902eac65d0..5f3580b165e 100644
--- a/src/EFCore/Infrastructure/ModelValidator.cs
+++ b/src/EFCore/Infrastructure/ModelValidator.cs
@@ -875,7 +875,7 @@ protected virtual void ValidateTypeMappings(
                 {
                     _ = property.GetCurrentValueComparer(); // Will throw if there is no way to compare
                 }
-                
+
                 var providerComparer = property.GetProviderValueComparer();
                 if (providerComparer == null)
                 {
diff --git a/src/EFCore/Storage/CoreTypeMapping.cs b/src/EFCore/Storage/CoreTypeMapping.cs
index d80348b4984..368914fb408 100644
--- a/src/EFCore/Storage/CoreTypeMapping.cs
+++ b/src/EFCore/Storage/CoreTypeMapping.cs
@@ -200,7 +200,7 @@ public virtual ValueComparer ProviderValueComparer
             this,
             static c => (c.Converter?.ProviderClrType ?? c.ClrType) == c.ClrType
                     ? c.KeyComparer
-                    : ValueComparer.CreateDefault(c.Converter?.ProviderClrType ?? c.ClrType, favorStructuralComparisons: true));
+                    : ValueComparer.CreateDefault(c.Converter!.ProviderClrType, favorStructuralComparisons: true));
 
     /// <summary>
     ///     Returns a new copy of this type mapping with the given <see cref="ValueConverter" />
diff --git a/test/EFCore.Tests/Infrastructure/ModelValidatorTest.cs b/test/EFCore.Tests/Infrastructure/ModelValidatorTest.cs
index 2fa187fea19..f3f63e1b31b 100644
--- a/test/EFCore.Tests/Infrastructure/ModelValidatorTest.cs
+++ b/test/EFCore.Tests/Infrastructure/ModelValidatorTest.cs
@@ -33,6 +33,50 @@ protected class WithNonComparableKey
         public NotComparable Id { get; set; }
     }
 
+    [ConditionalFact]
+    public virtual void Detects_noncomparable_key_property_with_comparer()
+    {
+        var modelBuilder = CreateConventionModelBuilder();
+
+        modelBuilder.Entity<WithNonComparableKey>(
+            eb =>
+            {
+                eb.Property(e => e.Id).HasConversion(typeof(NotComparable), typeof(CustomValueComparer<NotComparable>));
+                eb.HasKey(e => e.Id);
+            });
+
+        VerifyError(
+            CoreStrings.NonComparableKeyType(nameof(WithNonComparableKey), nameof(WithNonComparableKey.Id), nameof(NotComparable)),
+            modelBuilder);
+    }
+
+    [ConditionalFact]
+    public virtual void Detects_noncomparable_key_property_with_provider_comparer()
+    {
+        var modelBuilder = CreateConventionModelBuilder();
+
+        modelBuilder.Entity<WithNonComparableKey>(
+            eb =>
+            {
+                eb.Property(e => e.Id).HasConversion(
+                    typeof(CastingConverter<NotComparable, NotComparable>), null, typeof(CustomValueComparer<NotComparable>));
+                eb.HasKey(e => e.Id);
+            });
+
+        VerifyError(
+            CoreStrings.NonComparableKeyTypes(
+                nameof(WithNonComparableKey), nameof(WithNonComparableKey.Id), nameof(NotComparable), nameof(NotComparable)),
+            modelBuilder);
+    }
+
+    public class CustomValueComparer<T> : ValueComparer<T> // Doesn't implement IComparer
+    {
+        public CustomValueComparer()
+            : base(false)
+        {
+        }
+    }
+
     [ConditionalFact]
     public virtual void Detects_unique_index_property_which_cannot_be_compared()
     {
@@ -1396,7 +1440,7 @@ public virtual void Detects_incompatible_discriminator_value()
 
         VerifyError(CoreStrings.DiscriminatorValueIncompatible("1", nameof(A), "int"), modelBuilder);
     }
-    
+
     [ConditionalFact]
     public virtual void Detects_missing_discriminator_value_on_base()
     {
@@ -1412,7 +1456,7 @@ public virtual void Detects_missing_discriminator_value_on_base()
 
         entityA.SetDiscriminatorProperty(entityA.AddProperty("D", typeof(int)));
         entityA.RemoveDiscriminatorValue();
-        
+
         entityC.SetDiscriminatorValue(1);
 
         VerifyError(CoreStrings.NoDiscriminatorValue(entityA.DisplayName()), modelBuilder);
@@ -1433,7 +1477,7 @@ public virtual void Detects_missing_discriminator_value_on_leaf()
 
         entityAbstract.SetDiscriminatorProperty(entityAbstract.AddProperty("D", typeof(int)));
         entityAbstract.SetDiscriminatorValue(0);
-        
+
         entityGeneric.RemoveDiscriminatorValue();
 
         VerifyError(CoreStrings.NoDiscriminatorValue(entityGeneric.DisplayName()), modelBuilder);
diff --git a/test/EFCore.Tests/ModelBuilding/ModelBuilderGenericTest.cs b/test/EFCore.Tests/ModelBuilding/ModelBuilderGenericTest.cs
index a7727e3a1ae..0af74d7cd1c 100644
--- a/test/EFCore.Tests/ModelBuilding/ModelBuilderGenericTest.cs
+++ b/test/EFCore.Tests/ModelBuilding/ModelBuilderGenericTest.cs
@@ -517,14 +517,14 @@ public override TestPropertyBuilder<TProperty> HasField(string fieldName)
         public override TestPropertyBuilder<TProperty> UsePropertyAccessMode(PropertyAccessMode propertyAccessMode)
             => Wrap(PropertyBuilder.UsePropertyAccessMode(propertyAccessMode));
 
-        public override TestPropertyBuilder<TProperty> HasConversion<TProvider>()
-            => Wrap(PropertyBuilder.HasConversion<TProvider>());
+        public override TestPropertyBuilder<TProperty> HasConversion<TConversion>()
+            => Wrap(PropertyBuilder.HasConversion<TConversion>());
 
-        public override TestPropertyBuilder<TProperty> HasConversion<TProvider>(ValueComparer? valueComparer)
-            => Wrap(PropertyBuilder.HasConversion<TProvider>(valueComparer));
+        public override TestPropertyBuilder<TProperty> HasConversion<TConversion>(ValueComparer? valueComparer)
+            => Wrap(PropertyBuilder.HasConversion<TConversion>(valueComparer));
 
-        public override TestPropertyBuilder<TProperty> HasConversion<TProvider>(ValueComparer? valueComparer, ValueComparer? providerComparerType)
-            => Wrap(PropertyBuilder.HasConversion<TProvider>(valueComparer, providerComparerType));
+        public override TestPropertyBuilder<TProperty> HasConversion<TConversion>(ValueComparer? valueComparer, ValueComparer? providerComparerType)
+            => Wrap(PropertyBuilder.HasConversion<TConversion>(valueComparer, providerComparerType));
 
         public override TestPropertyBuilder<TProperty> HasConversion<TProvider>(
             Expression<Func<TProperty, TProvider>> convertToProviderExpression,
diff --git a/test/EFCore.Tests/ModelBuilding/ModelBuilderNonGenericTest.cs b/test/EFCore.Tests/ModelBuilding/ModelBuilderNonGenericTest.cs
index 72339a741ec..0461bb82e30 100644
--- a/test/EFCore.Tests/ModelBuilding/ModelBuilderNonGenericTest.cs
+++ b/test/EFCore.Tests/ModelBuilding/ModelBuilderNonGenericTest.cs
@@ -597,14 +597,14 @@ public override TestPropertyBuilder<TProperty> HasField(string fieldName)
         public override TestPropertyBuilder<TProperty> UsePropertyAccessMode(PropertyAccessMode propertyAccessMode)
             => Wrap(PropertyBuilder.UsePropertyAccessMode(propertyAccessMode));
 
-        public override TestPropertyBuilder<TProperty> HasConversion<TProvider>()
-            => Wrap(PropertyBuilder.HasConversion<TProvider>());
+        public override TestPropertyBuilder<TProperty> HasConversion<TConversion>()
+            => Wrap(PropertyBuilder.HasConversion(typeof(TConversion)));
 
-        public override TestPropertyBuilder<TProperty> HasConversion<TProvider>(ValueComparer? valueComparer)
-            => Wrap(PropertyBuilder.HasConversion<TProvider>(valueComparer));
+        public override TestPropertyBuilder<TProperty> HasConversion<TConversion>(ValueComparer? valueComparer)
+            => Wrap(PropertyBuilder.HasConversion(typeof(TConversion), valueComparer));
 
-        public override TestPropertyBuilder<TProperty> HasConversion<TProvider>(ValueComparer? valueComparer, ValueComparer? providerComparerType)
-            => Wrap(PropertyBuilder.HasConversion<TProvider>(valueComparer, providerComparerType));
+        public override TestPropertyBuilder<TProperty> HasConversion<TConversion>(ValueComparer? valueComparer, ValueComparer? providerComparerType)
+            => Wrap(PropertyBuilder.HasConversion(typeof(TConversion), valueComparer, providerComparerType));
 
         public override TestPropertyBuilder<TProperty> HasConversion<TProvider>(
             Expression<Func<TProperty, TProvider>> convertToProviderExpression,
diff --git a/test/EFCore.Tests/ModelBuilding/ModelBuilderTestBase.cs b/test/EFCore.Tests/ModelBuilding/ModelBuilderTestBase.cs
index bd7ee7ac3d5..f796983df96 100644
--- a/test/EFCore.Tests/ModelBuilding/ModelBuilderTestBase.cs
+++ b/test/EFCore.Tests/ModelBuilding/ModelBuilderTestBase.cs
@@ -400,9 +400,9 @@ public abstract TestPropertyBuilder<TProperty> HasValueGeneratorFactory<TFactory
         public abstract TestPropertyBuilder<TProperty> HasField(string fieldName);
         public abstract TestPropertyBuilder<TProperty> UsePropertyAccessMode(PropertyAccessMode propertyAccessMode);
 
-        public abstract TestPropertyBuilder<TProperty> HasConversion<TProvider>();
-        public abstract TestPropertyBuilder<TProperty> HasConversion<TProvider>(ValueComparer? valueComparer);
-        public abstract TestPropertyBuilder<TProperty> HasConversion<TProvider>(ValueComparer? valueComparer, ValueComparer? providerComparerType);
+        public abstract TestPropertyBuilder<TProperty> HasConversion<TConversion>();
+        public abstract TestPropertyBuilder<TProperty> HasConversion<TConversion>(ValueComparer? valueComparer);
+        public abstract TestPropertyBuilder<TProperty> HasConversion<TConversion>(ValueComparer? valueComparer, ValueComparer? providerComparerType);
 
         public abstract TestPropertyBuilder<TProperty> HasConversion<TProvider>(
             Expression<Func<TProperty, TProvider>> convertToProviderExpression,