diff --git a/OpenMcdf.Ole/DictionaryProperty.cs b/OpenMcdf.Ole/DictionaryProperty.cs
index cff15a5..c631d3a 100644
--- a/OpenMcdf.Ole/DictionaryProperty.cs
+++ b/OpenMcdf.Ole/DictionaryProperty.cs
@@ -2,7 +2,7 @@
 
 namespace OpenMcdf.Ole;
 
-public sealed class DictionaryProperty : IProperty
+internal sealed class DictionaryProperty : IProperty
 {
     private readonly int codePage;
     private Dictionary<uint, string>? entries = new();
diff --git a/OpenMcdf.Ole/IProperty.cs b/OpenMcdf.Ole/IProperty.cs
index 6e9e261..b034f20 100644
--- a/OpenMcdf.Ole/IProperty.cs
+++ b/OpenMcdf.Ole/IProperty.cs
@@ -1,12 +1,12 @@
 namespace OpenMcdf.Ole;
 
-public enum PropertyType
+internal enum PropertyType
 {
     TypedPropertyValue = 0,
     DictionaryProperty = 1
 }
 
-public interface IProperty : IBinarySerializable
+internal interface IProperty : IBinarySerializable
 {
     object? Value { get; set; }
 
diff --git a/OpenMcdf.Ole/ITypedPropertyValue.cs b/OpenMcdf.Ole/ITypedPropertyValue.cs
index 94c4c5a..a2d0039 100644
--- a/OpenMcdf.Ole/ITypedPropertyValue.cs
+++ b/OpenMcdf.Ole/ITypedPropertyValue.cs
@@ -7,7 +7,7 @@ public enum PropertyDimensions
     IsArray
 }
 
-public interface ITypedPropertyValue : IProperty
+internal interface ITypedPropertyValue : IProperty
 {
     VTPropertyType VTType { get; }