diff --git a/YamlDotNet/Serialization/TypeInspectors/CachedTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/CachedTypeInspector.cs
index 743b3b55..80cbe5ef 100644
--- a/YamlDotNet/Serialization/TypeInspectors/CachedTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/CachedTypeInspector.cs
@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Wraps another <see cref="ITypeInspector"/> and applies caching.
     /// </summary>
-    public sealed class CachedTypeInspector : TypeInspectorSkeleton
+    public class CachedTypeInspector : TypeInspectorSkeleton
     {
         private readonly ITypeInspector innerTypeDescriptor;
         private readonly ConcurrentDictionary<Type, List<IPropertyDescriptor>> cache = new ConcurrentDictionary<Type, List<IPropertyDescriptor>>();
diff --git a/YamlDotNet/Serialization/TypeInspectors/CompositeTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/CompositeTypeInspector.cs
index af366e69..53c1c80b 100644
--- a/YamlDotNet/Serialization/TypeInspectors/CompositeTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/CompositeTypeInspector.cs
@@ -28,7 +28,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Aggregates the results from multiple <see cref="ITypeInspector" /> into a single one.
     /// </summary>
-    public sealed class CompositeTypeInspector : TypeInspectorSkeleton
+    public class CompositeTypeInspector : TypeInspectorSkeleton
     {
         private readonly IEnumerable<ITypeInspector> typeInspectors;
 
diff --git a/YamlDotNet/Serialization/TypeInspectors/NamingConventionTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/NamingConventionTypeInspector.cs
index 5a4356ab..c77bd003 100644
--- a/YamlDotNet/Serialization/TypeInspectors/NamingConventionTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/NamingConventionTypeInspector.cs
@@ -29,7 +29,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// Wraps another <see cref="ITypeInspector"/> and applies a
     /// naming convention to the names of the properties.
     /// </summary>
-    public sealed class NamingConventionTypeInspector : TypeInspectorSkeleton
+    public class NamingConventionTypeInspector : TypeInspectorSkeleton
     {
         private readonly ITypeInspector innerTypeDescriptor;
         private readonly INamingConvention namingConvention;
diff --git a/YamlDotNet/Serialization/TypeInspectors/ReadableAndWritablePropertiesTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/ReadableAndWritablePropertiesTypeInspector.cs
index d2418af6..9eac967c 100644
--- a/YamlDotNet/Serialization/TypeInspectors/ReadableAndWritablePropertiesTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/ReadableAndWritablePropertiesTypeInspector.cs
@@ -28,7 +28,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties of a type that are both readable and writable.
     /// </summary>
-    public sealed class ReadableAndWritablePropertiesTypeInspector : TypeInspectorSkeleton
+    public class ReadableAndWritablePropertiesTypeInspector : TypeInspectorSkeleton
     {
         private readonly ITypeInspector innerTypeDescriptor;
 
diff --git a/YamlDotNet/Serialization/TypeInspectors/ReadableFieldsTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/ReadableFieldsTypeInspector.cs
index 51fbb3d0..e779f2aa 100644
--- a/YamlDotNet/Serialization/TypeInspectors/ReadableFieldsTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/ReadableFieldsTypeInspector.cs
@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties and fields of a type that are readable.
     /// </summary>
-    public sealed class ReadableFieldsTypeInspector : ReflectionTypeInspector
+    public class ReadableFieldsTypeInspector : ReflectionTypeInspector
     {
         private readonly ITypeResolver typeResolver;
 
@@ -46,7 +46,7 @@ public override IEnumerable<IPropertyDescriptor> GetProperties(Type type, object
                 .Select(p => (IPropertyDescriptor)new ReflectionFieldDescriptor(p, typeResolver));
         }
 
-        private sealed class ReflectionFieldDescriptor : IPropertyDescriptor
+        protected class ReflectionFieldDescriptor : IPropertyDescriptor
         {
             private readonly FieldInfo fieldInfo;
             private readonly ITypeResolver typeResolver;
diff --git a/YamlDotNet/Serialization/TypeInspectors/ReadablePropertiesTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/ReadablePropertiesTypeInspector.cs
index 903781e4..e578d522 100644
--- a/YamlDotNet/Serialization/TypeInspectors/ReadablePropertiesTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/ReadablePropertiesTypeInspector.cs
@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties of a type that are readable.
     /// </summary>
-    public sealed class ReadablePropertiesTypeInspector : ReflectionTypeInspector
+    public class ReadablePropertiesTypeInspector : ReflectionTypeInspector
     {
         private readonly ITypeResolver typeResolver;
         private readonly bool includeNonPublicProperties;
@@ -60,7 +60,7 @@ public override IEnumerable<IPropertyDescriptor> GetProperties(Type type, object
                 .Select(p => (IPropertyDescriptor)new ReflectionPropertyDescriptor(p, typeResolver));
         }
 
-        private sealed class ReflectionPropertyDescriptor : IPropertyDescriptor
+        protected class ReflectionPropertyDescriptor : IPropertyDescriptor
         {
             private readonly PropertyInfo propertyInfo;
             private readonly ITypeResolver typeResolver;
diff --git a/YamlDotNet/Serialization/TypeInspectors/WritablePropertiesTypeInspector.cs b/YamlDotNet/Serialization/TypeInspectors/WritablePropertiesTypeInspector.cs
index 2111f059..2b9a6897 100644
--- a/YamlDotNet/Serialization/TypeInspectors/WritablePropertiesTypeInspector.cs
+++ b/YamlDotNet/Serialization/TypeInspectors/WritablePropertiesTypeInspector.cs
@@ -30,7 +30,7 @@ namespace YamlDotNet.Serialization.TypeInspectors
     /// <summary>
     /// Returns the properties of a type that are writable.
     /// </summary>
-    public sealed class WritablePropertiesTypeInspector : ReflectionTypeInspector
+    public class WritablePropertiesTypeInspector : ReflectionTypeInspector
     {
         private readonly ITypeResolver typeResolver;
         private readonly bool includeNonPublicProperties;
@@ -61,7 +61,7 @@ public override IEnumerable<IPropertyDescriptor> GetProperties(Type type, object
                 .ToArray();
         }
 
-        private sealed class ReflectionPropertyDescriptor : IPropertyDescriptor
+        protected class ReflectionPropertyDescriptor : IPropertyDescriptor
         {
             private readonly PropertyInfo propertyInfo;
             private readonly ITypeResolver typeResolver;