diff --git a/Svelto.ECS/EnginesRoot.Entities.cs b/Svelto.ECS/EnginesRoot.Entities.cs
index daf07eb..c022223 100644
--- a/Svelto.ECS/EnginesRoot.Entities.cs
+++ b/Svelto.ECS/EnginesRoot.Entities.cs
@@ -37,17 +37,18 @@ namespace Svelto.ECS
         ///--------------------------------------------
 
         EntityStructInitializer BuildEntity<T>(EGID entityID, object[] implementors)
-            where T : class, IEntityDescriptor, new()
+            where T : IEntityDescriptor, new()
         {
             var dic = EntityFactory.BuildGroupedEntityViews(entityID,
-                                                  _groupedEntityToAdd.current,
-                                                  EntityDescriptorTemplate<T>.Info.entityViewsToBuild,
-                                                  implementors);
+                              _groupedEntityToAdd.current,
+                              EntityDescriptorTemplate<T>.Info.entityViewsToBuild,
+                              implementors);
             
             return new EntityStructInitializer(entityID, dic);
         }
 
-        EntityStructInitializer BuildEntity(EGID entityID, IEntityViewBuilder[] entityViewsToBuild,
+        EntityStructInitializer BuildEntity(EGID entityID, 
+                                IEntityViewBuilder[] entityViewsToBuild,
                                 object[] implementors)
         {
             var dic = EntityFactory.BuildGroupedEntityViews(entityID,
@@ -60,7 +61,7 @@ namespace Svelto.ECS
 
         ///--------------------------------------------
 
-        void Preallocate<T>(int groupID, int size) where T : class, IEntityDescriptor, new()
+        void Preallocate<T>(int groupID, int size) where T : IEntityDescriptor, new()
         {
             var entityViewsToBuild = EntityDescriptorTemplate<T>.Info.entityViewsToBuild;
             var count              = entityViewsToBuild.Length;
@@ -209,7 +210,7 @@ namespace Svelto.ECS
             _id = id;
         }
 
-        public void Init<T>(ref T initializer) where T: struct, IEntityStruct
+        public void Init<T>(T initializer) where T: struct, IEntityStruct
         {
             var typeSafeDictionary = (TypeSafeDictionary<T>) _current[typeof(T)];
 
diff --git a/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs b/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs
index ab048bd..9c0a983 100644
--- a/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs
+++ b/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs
@@ -17,17 +17,17 @@ namespace Svelto.ECS
                 _weakEngine = weakReference;
             }
 
-            public EntityStructInitializer BuildEntity<T>(int entityID, object[] implementors) where T : class, IEntityDescriptor, new()
+            public EntityStructInitializer BuildEntity<T>(int entityID, object[] implementors) where T : IEntityDescriptor, new()
             {
                 return _weakEngine.Target.BuildEntity<T>(new EGID(entityID), implementors);
             }
 
-            public EntityStructInitializer BuildEntity<T>(int entityID, int groupID, object[] implementors) where T : class, IEntityDescriptor, new()
+            public EntityStructInitializer BuildEntity<T>(int entityID, int groupID, object[] implementors) where T : IEntityDescriptor, new()
             {
                 return _weakEngine.Target.BuildEntity<T>(new EGID(entityID, groupID), implementors);
             }
 
-            public EntityStructInitializer BuildEntity<T>(EGID egid, object[] implementors) where T : class, IEntityDescriptor, new()
+            public EntityStructInitializer BuildEntity<T>(EGID egid, object[] implementors) where T : IEntityDescriptor, new()
             {
                 return _weakEngine.Target.BuildEntity<T>(egid, implementors);
             }
@@ -47,12 +47,12 @@ namespace Svelto.ECS
                 return _weakEngine.Target.BuildEntity(new EGID(entityID, groupID), entityViewsToBuild, implementors);
             }
             
-            public void PreallocateEntitySpace<T>(int size) where T : class, IEntityDescriptor, new()
+            public void PreallocateEntitySpace<T>(int size) where T : IEntityDescriptor, new()
             {
                 _weakEngine.Target.Preallocate<T>(ExclusiveGroups.StandardEntity, size);
             }
             
-            public void PreallocateEntitySpace<T>(int groupID, int size) where T : class, IEntityDescriptor, new()
+            public void PreallocateEntitySpace<T>(int groupID, int size) where T : IEntityDescriptor, new()
             {
                 _weakEngine.Target.Preallocate<T>(groupID, size);
             }
diff --git a/Svelto.ECS/EntityDescriptor.cs b/Svelto.ECS/EntityDescriptor.cs
index db1bc4c..f0bc7b0 100644
--- a/Svelto.ECS/EntityDescriptor.cs
+++ b/Svelto.ECS/EntityDescriptor.cs
@@ -18,9 +18,9 @@ namespace Svelto.ECS
         public IEntityViewBuilder[] entityViewsToBuild { get; }
     }
 
-    public static class EntityDescriptorTemplate<TType> where TType : class, IEntityDescriptor, new()
+    public static class EntityDescriptorTemplate<TType> where TType : IEntityDescriptor, new()
     {
-        public static readonly EntityDescriptorInfo Info = new EntityDescriptorInfo(new TType());
+        public static readonly EntityDescriptorInfo<TType> Info = new EntityDescriptorInfo<TType>(new TType());
     }
 
     public struct DynamicEntityDescriptorInfo<TType> where TType : class, IEntityDescriptor, new()
@@ -42,11 +42,11 @@ namespace Svelto.ECS
         }
     }
 
-    public struct EntityDescriptorInfo
+    public struct EntityDescriptorInfo<TType> where TType : IEntityDescriptor
     {
         public readonly IEntityViewBuilder[] entityViewsToBuild;
 
-        internal EntityDescriptorInfo(IEntityDescriptor descriptor)
+        internal EntityDescriptorInfo(TType descriptor)
         {
             entityViewsToBuild = descriptor.entityViewsToBuild;
         }
diff --git a/Svelto.ECS/EntityViewsDB.cs b/Svelto.ECS/EntityViewsDB.cs
index 66268ce..60515c8 100644
--- a/Svelto.ECS/EntityViewsDB.cs
+++ b/Svelto.ECS/EntityViewsDB.cs
@@ -71,7 +71,7 @@ namespace Svelto.ECS.Internal
 
             int count;
             
-            return QueryEntities<T>(out count);
+            return QueryEntities<T>(entityGID.groupID, out count);
         }
 
         public T QueryEntityView<T>(EGID entityGID) where T : class, IEntityStruct
diff --git a/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs b/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs
index bf48b5e..78d6e1f 100644
--- a/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs
+++ b/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs
@@ -5,7 +5,7 @@ namespace Svelto.ECS
         UnityEngine.MonoBehaviour , IEntityDescriptorHolder
             where T: class, IEntityDescriptor, new()
     {
-        public EntityDescriptorInfo RetrieveDescriptorInfo()
+        public EntityDescriptorInfo<T> RetrieveDescriptorInfo<T>()
         {
             return EntityDescriptorTemplate<T>.Info;
         }
diff --git a/Svelto.ECS/IEntityDescriptorHolder.cs b/Svelto.ECS/IEntityDescriptorHolder.cs
index 6b5dac5..785c5fb 100644
--- a/Svelto.ECS/IEntityDescriptorHolder.cs
+++ b/Svelto.ECS/IEntityDescriptorHolder.cs
@@ -2,6 +2,6 @@ namespace Svelto.ECS
 {
     public interface IEntityDescriptorHolder
     {
-        EntityDescriptorInfo RetrieveDescriptorInfo();
+        EntityDescriptorInfo<T> RetrieveDescriptorInfo<T>() where T : IEntityDescriptor;
     }
 }
\ No newline at end of file
diff --git a/Svelto.ECS/IEntityFactory.cs b/Svelto.ECS/IEntityFactory.cs
index 46cb2b3..aab3420 100644
--- a/Svelto.ECS/IEntityFactory.cs
+++ b/Svelto.ECS/IEntityFactory.cs
@@ -16,8 +16,8 @@ namespace Svelto.ECS
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="size"></param>
-        void PreallocateEntitySpace<T>(int size) where T : class, IEntityDescriptor, new();
-        void PreallocateEntitySpace<T>(int groupID, int size) where T : class, IEntityDescriptor, new();
+        void PreallocateEntitySpace<T>(int size) where T : IEntityDescriptor, new();
+        void PreallocateEntitySpace<T>(int groupID, int size) where T : IEntityDescriptor, new();
         
         /// <summary>
         ///     The EntityDescriptor doesn't need to be ever instantiated. It just describes the Entity
@@ -28,7 +28,7 @@ namespace Svelto.ECS
         /// <typeparam name="T"></typeparam>
         /// <param name="entityID"></param>
         /// <param name="implementors"></param>
-        EntityStructInitializer BuildEntity<T>(int entityID, object[] implementors) where T:class, IEntityDescriptor, new();
+        EntityStructInitializer BuildEntity<T>(int entityID, object[] implementors) where T:IEntityDescriptor, new();
 
 
         /// <summary>
@@ -41,8 +41,8 @@ namespace Svelto.ECS
         /// <param name="groupID"></param>
         /// <param name="ed"></param>
         /// <param name="implementors"></param>
-        EntityStructInitializer BuildEntity<T>(int entityID, int groupID, object[] implementors) where T:class, IEntityDescriptor, new();
-        EntityStructInitializer BuildEntity<T>(EGID egid, object[] implementors) where T:class, IEntityDescriptor, new();
+        EntityStructInitializer BuildEntity<T>(int entityID, int groupID, object[] implementors) where T:IEntityDescriptor, new();
+        EntityStructInitializer BuildEntity<T>(EGID egid, object[] implementors) where T:IEntityDescriptor, new();
         
 
         /// <summary>