diff --git a/Dapper/CustomPropertyTypeMap.cs b/Dapper/CustomPropertyTypeMap.cs
index 0d36f7470..919e561df 100644
--- a/Dapper/CustomPropertyTypeMap.cs
+++ b/Dapper/CustomPropertyTypeMap.cs
@@ -9,14 +9,14 @@ namespace Dapper
     public sealed class CustomPropertyTypeMap : SqlMapper.ITypeMap
     {
         private readonly Type _type;
-        private readonly Func<Type, string, PropertyInfo> _propertySelector;
+        private readonly Func<Type, string, PropertyInfo?> _propertySelector;
 
         /// <summary>
         /// Creates custom property mapping
         /// </summary>
         /// <param name="type">Target entity type</param>
         /// <param name="propertySelector">Property selector based on target type and DataReader column name</param>
-        public CustomPropertyTypeMap(Type type, Func<Type, string, PropertyInfo> propertySelector)
+        public CustomPropertyTypeMap(Type type, Func<Type, string, PropertyInfo?> propertySelector)
         {
             _type = type ?? throw new ArgumentNullException(nameof(type));
             _propertySelector = propertySelector ?? throw new ArgumentNullException(nameof(propertySelector));
diff --git a/Dapper/PublicAPI.Shipped.txt b/Dapper/PublicAPI.Shipped.txt
index c1b08ea99..5428f0eca 100644
--- a/Dapper/PublicAPI.Shipped.txt
+++ b/Dapper/PublicAPI.Shipped.txt
@@ -22,7 +22,7 @@ Dapper.CommandFlags.NoCache = 4 -> Dapper.CommandFlags
 Dapper.CommandFlags.None = 0 -> Dapper.CommandFlags
 Dapper.CommandFlags.Pipelined = 2 -> Dapper.CommandFlags
 Dapper.CustomPropertyTypeMap
-Dapper.CustomPropertyTypeMap.CustomPropertyTypeMap(System.Type! type, System.Func<System.Type!, string!, System.Reflection.PropertyInfo!>! propertySelector) -> void
+Dapper.CustomPropertyTypeMap.CustomPropertyTypeMap(System.Type! type, System.Func<System.Type!, string!, System.Reflection.PropertyInfo?>! propertySelector) -> void
 Dapper.CustomPropertyTypeMap.FindConstructor(string![]! names, System.Type![]! types) -> System.Reflection.ConstructorInfo?
 Dapper.CustomPropertyTypeMap.FindExplicitConstructor() -> System.Reflection.ConstructorInfo?
 Dapper.CustomPropertyTypeMap.GetConstructorParameter(System.Reflection.ConstructorInfo! constructor, string! columnName) -> Dapper.SqlMapper.IMemberMap!
diff --git a/tests/Dapper.Tests/TypeHandlerTests.cs b/tests/Dapper.Tests/TypeHandlerTests.cs
index 2e754ca46..7dc41389a 100644
--- a/tests/Dapper.Tests/TypeHandlerTests.cs
+++ b/tests/Dapper.Tests/TypeHandlerTests.cs
@@ -59,7 +59,7 @@ public void TestChangingDefaultStringTypeMappingToAnsiStringFirstOrDefault()
         public void TestCustomTypeMap()
         {
             // default mapping
-            var item = connection.Query<TypeWithMapping>("Select 'AVal' as A, 'BVal' as B").Single();
+            var item = connection.Query<TypeWithMapping>("Select 'AVal' as A, 'BVal' as B, 'CVal' as C").Single();
             Assert.Equal("AVal", item.A);
             Assert.Equal("BVal", item.B);
 
@@ -68,13 +68,13 @@ public void TestCustomTypeMap()
                 (type, columnName) => type.GetProperties().FirstOrDefault(prop => GetDescriptionFromAttribute(prop) == columnName)!);
             SqlMapper.SetTypeMap(typeof(TypeWithMapping), map);
 
-            item = connection.Query<TypeWithMapping>("Select 'AVal' as A, 'BVal' as B").Single();
+            item = connection.Query<TypeWithMapping>("Select 'AVal' as A, 'BVal' as B, 'CVal' as C").Single();
             Assert.Equal("BVal", item.A);
             Assert.Equal("AVal", item.B);
 
             // reset to default
             SqlMapper.SetTypeMap(typeof(TypeWithMapping), null);
-            item = connection.Query<TypeWithMapping>("Select 'AVal' as A, 'BVal' as B").Single();
+            item = connection.Query<TypeWithMapping>("Select 'AVal' as A, 'BVal' as B, 'CVal' as C").Single();
             Assert.Equal("AVal", item.A);
             Assert.Equal("BVal", item.B);
         }