diff --git a/src/MongODM.Core/Serialization/Mapping/CustomSerializerMap.cs b/src/MongODM.Core/Serialization/Mapping/CustomSerializerMap.cs
index dd9845c..9847ef0 100644
--- a/src/MongODM.Core/Serialization/Mapping/CustomSerializerMap.cs
+++ b/src/MongODM.Core/Serialization/Mapping/CustomSerializerMap.cs
@@ -18,7 +18,6 @@
 namespace Etherna.MongODM.Core.Serialization.Mapping
 {
     internal sealed class CustomSerializerMap<TModel> : MapBase, ICustomSerializerMapBuilder<TModel>
-        where TModel : class
     {
         // Constructor.
         public CustomSerializerMap(
diff --git a/src/MongODM.Core/Serialization/Mapping/ICustomSerializerMapBuilder.cs b/src/MongODM.Core/Serialization/Mapping/ICustomSerializerMapBuilder.cs
index 5bef944..c9493d9 100644
--- a/src/MongODM.Core/Serialization/Mapping/ICustomSerializerMapBuilder.cs
+++ b/src/MongODM.Core/Serialization/Mapping/ICustomSerializerMapBuilder.cs
@@ -15,7 +15,6 @@
 namespace Etherna.MongODM.Core.Serialization.Mapping
 {
     public interface ICustomSerializerMapBuilder<TModel>
-        where TModel : class
     {
     }
 }
\ No newline at end of file
diff --git a/src/MongODM.Core/Serialization/Mapping/IMapRegistry.cs b/src/MongODM.Core/Serialization/Mapping/IMapRegistry.cs
index 9197e8b..efafd92 100644
--- a/src/MongODM.Core/Serialization/Mapping/IMapRegistry.cs
+++ b/src/MongODM.Core/Serialization/Mapping/IMapRegistry.cs
@@ -42,8 +42,7 @@ public interface IMapRegistry : IDbContextInitializable, IFreezableConfig
         /// <param name="customSerializer">Custom serializer</param>
         /// <returns>The new schema</returns>
         ICustomSerializerMapBuilder<TModel> AddCustomSerializerMap<TModel>(
-            IBsonSerializer<TModel> customSerializer)
-            where TModel : class;
+            IBsonSerializer<TModel> customSerializer);
 
         /// <summary>
         /// Register a new schema based on model map
@@ -56,8 +55,7 @@ ICustomSerializerMapBuilder<TModel> AddCustomSerializerMap<TModel>(
         IModelMapBuilder<TModel> AddModelMap<TModel>(
             string activeModelMapSchemaId,
             Action<BsonClassMap<TModel>>? activeModelMapSchemaInitializer = null,
-            IBsonSerializer<TModel>? customSerializer = null)
-            where TModel : class;
+            IBsonSerializer<TModel>? customSerializer = null);
 
         /// <summary>
         /// Get active class map from schemas, or create a default classMap for model type
diff --git a/src/MongODM.Core/Serialization/Mapping/MapRegistry.cs b/src/MongODM.Core/Serialization/Mapping/MapRegistry.cs
index 42ea182..c5bfb9e 100644
--- a/src/MongODM.Core/Serialization/Mapping/MapRegistry.cs
+++ b/src/MongODM.Core/Serialization/Mapping/MapRegistry.cs
@@ -59,7 +59,7 @@ public void Initialize(IDbContext dbContext, ILogger logger)
 
         // Methods.
         public ICustomSerializerMapBuilder<TModel> AddCustomSerializerMap<TModel>(
-            IBsonSerializer<TModel> customSerializer) where TModel : class =>
+            IBsonSerializer<TModel> customSerializer) =>
             ExecuteConfigAction(() =>
             {
                 ArgumentNullException.ThrowIfNull(customSerializer, nameof(customSerializer));
@@ -74,8 +74,7 @@ public ICustomSerializerMapBuilder<TModel> AddCustomSerializerMap<TModel>(
         public IModelMapBuilder<TModel> AddModelMap<TModel>(
             string activeModelMapSchemaId,
             Action<BsonClassMap<TModel>>? activeModelMapSchemaInitializer = null,
-            IBsonSerializer<TModel>? customSerializer = null)
-            where TModel : class =>
+            IBsonSerializer<TModel>? customSerializer = null) =>
             ExecuteConfigAction(() =>
             {
                 // Register and add schema configuration.
diff --git a/src/MongODM.Core/Serialization/Mapping/ModelMap.cs b/src/MongODM.Core/Serialization/Mapping/ModelMap.cs
index d6f7d2d..5e48cca 100644
--- a/src/MongODM.Core/Serialization/Mapping/ModelMap.cs
+++ b/src/MongODM.Core/Serialization/Mapping/ModelMap.cs
@@ -38,8 +38,9 @@ protected ModelMap(
         {
             DbContext = dbContext ?? throw new ArgumentNullException(nameof(dbContext));
 
-            // Verify if have to use proxy model.
-            if (modelType != typeof(object) &&
+            // Verify if uses proxy model.
+            if (modelType.IsClass &&
+                modelType != typeof(object) &&
                 !modelType.IsAbstract &&
                 !dbContext.ProxyGenerator.IsProxyType(modelType))
             {
@@ -202,7 +203,6 @@ private MemberMap BuildMemberMap(
 
     [SuppressMessage("Reliability", "CA2000:Dispose objects before losing scope")]
     internal sealed class ModelMap<TModel> : ModelMap, IModelMapBuilder<TModel>
-        where TModel : class
     {
         // Constructor.
         public ModelMap(IDbContext dbContext)
diff --git a/src/MongODM.Core/Serialization/Serializers/ModelMapSerializer.cs b/src/MongODM.Core/Serialization/Serializers/ModelMapSerializer.cs
index caeef61..add8e04 100644
--- a/src/MongODM.Core/Serialization/Serializers/ModelMapSerializer.cs
+++ b/src/MongODM.Core/Serialization/Serializers/ModelMapSerializer.cs
@@ -29,11 +29,9 @@ namespace Etherna.MongODM.Core.Serialization.Serializers
 {
     public class ModelMapSerializer<TModel> :
         SerializerBase<TModel>,
-        IBsonSerializer<TModel>,
         IBsonDocumentSerializer,
         IBsonIdProvider,
         IModelMapsHandlingSerializer
-        where TModel : class
     {
         // Fields.
         private IDiscriminatorConvention _discriminatorConvention = default!;
@@ -72,7 +70,7 @@ public override TModel Deserialize(BsonDeserializationContext context, BsonDeser
             if (context.Reader.CurrentBsonType == BsonType.Null)
             {
                 context.Reader.ReadNull();
-                return null!;
+                return default!;
             }
 
             // Find pre-deserialization informations.
@@ -139,15 +137,15 @@ public override TModel Deserialize(BsonDeserializationContext context, BsonDeser
              * In this case, don't add any not-proxy models in cache.
              */
             if (!dbContext.SerializerModifierAccessor.IsNoCacheEnabled &&
-                GetDocumentId(model, out var id, out _, out _) && id != null &&
-                dbContext.ProxyGenerator.IsProxyType(model.GetType()))
+                dbContext.ProxyGenerator.IsProxyType(model!.GetType()) &&
+                GetDocumentId(model, out var id, out _, out _) && id != null)
             {
                 if (dbContext.DbCache.LoadedModels.ContainsKey(id))
                 {
                     var fullModel = model;
                     model = (TModel)dbContext.DbCache.LoadedModels[id];
 
-                    if (((IReferenceable)model).IsSummary)
+                    if (((IReferenceable)model!).IsSummary)
                         ((IReferenceable)model).MergeFullModel(fullModel);
                 }
                 else