diff --git a/Svelto.ECS/Common/Components/ECSRect.cs b/Svelto.ECS/Common/Components/ECSRect.cs
index 29f2a54..13daa82 100644
--- a/Svelto.ECS/Common/Components/ECSRect.cs
+++ b/Svelto.ECS/Common/Components/ECSRect.cs
@@ -1,3 +1,4 @@
+#if UNITY_5 || UNITY_5_3_OR_NEWER
 using UnityEngine;
 
 namespace Svelto.ECS.Components
@@ -14,4 +15,5 @@ namespace Svelto.ECS.Components
             height = imageUvRect.height;
         }
     }
-}
\ No newline at end of file
+}
+#endif
diff --git a/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs b/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs
index 80312b6..6290e3b 100644
--- a/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs
+++ b/Svelto.ECS/Extensions/Unity/GenericEntityDescriptorHolder.cs
@@ -1,6 +1,6 @@
+#if UNITY_5 || UNITY_5_3_OR_NEWER
 using UnityEngine;
 
-#if UNITY_5 || UNITY_5_3_OR_NEWER
 namespace Svelto.ECS.Unity
 {
     public class GenericEntityDescriptorHolder<T>: