diff --git a/src/PetStore.Core/DomainObjects/Foundation/Category.cs b/src/PetStore.Core/DomainObjects/Foundation/Category.cs
index 4b628af..e34490f 100644
--- a/src/PetStore.Core/DomainObjects/Foundation/Category.cs
+++ b/src/PetStore.Core/DomainObjects/Foundation/Category.cs
@@ -10,17 +10,17 @@ public class Category
         /// <summary>
         /// Category ID
         /// </summary>
-        public int Id { get; set; }
+        public virtual int Id { get; set; }
 
         /// <summary>
         /// Category name
         /// </summary>
-        public string Name { get; set; }
+        public virtual string Name { get; set; }
 
         /// <summary>
         /// Category description
         /// </summary>
-        public string Description { get; set; }
+        public virtual string Description { get; set; }
 
         #endregion
     }
diff --git a/src/PetStore.Core/DomainObjects/Foundation/Country.cs b/src/PetStore.Core/DomainObjects/Foundation/Country.cs
index 8463241..93d3792 100644
--- a/src/PetStore.Core/DomainObjects/Foundation/Country.cs
+++ b/src/PetStore.Core/DomainObjects/Foundation/Country.cs
@@ -10,17 +10,17 @@ public class Country
         /// <summary>
         /// Country ID
         /// </summary>
-        public int Id { get; set; }
+        public virtual int Id { get; set; }
 
         /// <summary>
         /// Country name
         /// </summary>
-        public string Name { get; set; }
+        public virtual string Name { get; set; }
 
         /// <summary>
         /// Country code (acronym) defined on (ISO 3166-1 alfa-2)
         /// </summary>
-        public string Code { get; set; }
+        public virtual string Code { get; set; }
 
         #endregion
     }
diff --git a/src/PetStore.Core/DomainObjects/Foundation/Product.cs b/src/PetStore.Core/DomainObjects/Foundation/Product.cs
index 32edfb5..3f0c1c9 100644
--- a/src/PetStore.Core/DomainObjects/Foundation/Product.cs
+++ b/src/PetStore.Core/DomainObjects/Foundation/Product.cs
@@ -10,27 +10,27 @@ public class Product
         /// <summary>
         /// Product ID
         /// </summary>
-        public int Id { get; set; }
+        public virtual int Id { get; set; }
 
         /// <summary>
         /// Product category
         /// </summary>
-        public Category Category { get; set; }
+        public virtual Category Category { get; set; }
 
         /// <summary>
         /// Product name
         /// </summary>
-        public string Name { get; set; }
+        public virtual string Name { get; set; }
 
         /// <summary>
         /// Product description
         /// </summary>
-        public string Description { get; set; }
+        public virtual string Description { get; set; }
 
         /// <summary>
         /// Product image path
         /// </summary>
-        public string ImagePath { get; set; }
+        public virtual string ImagePath { get; set; }
 
         #endregion
     }