diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java
index baa1c8e5b..bbdd3ab6f 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/materials/AssignedMaterialsModel.java
@@ -83,6 +83,7 @@ public abstract class AssignedMaterialsModel<T, A> implements
     }
 
     protected void initializeMaterialCategory(MaterialCategory materialCategory) {
+        categoryDAO.reattach(materialCategory);
         materialCategory.getName();
         initializeMaterials(materialCategory.getMaterials());
         initializeMaterialCategories(materialCategory.getSubcategories());