diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java
index 3dd6ff31a..2dc7fcde3 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java
@@ -80,6 +80,8 @@ public class MaterialsController extends
 
     private Textbox txtCategory;
 
+    private Button btnAddMaterial;
+
     private IMessagesForUser messagesForUser;
 
     private Component messagesContainer;
@@ -268,7 +270,7 @@ public class MaterialsController extends
 
     public void addMaterialToMaterialCategory(Treeitem treeitem) {
         if (treeitem == null) {
-            return;
+            throw new WrongValueException(btnAddMaterial, _("Cannot insert material in general view. Please, select a category"));
         }
         final MaterialCategory materialCategory = (MaterialCategory) treeitem.getValue();
         materialsModel.addMaterialToMaterialCategory(materialCategory);
diff --git a/navalplanner-webapp/src/main/webapp/materials/materials.zul b/navalplanner-webapp/src/main/webapp/materials/materials.zul
index 389f5b416..7949713c9 100644
--- a/navalplanner-webapp/src/main/webapp/materials/materials.zul
+++ b/navalplanner-webapp/src/main/webapp/materials/materials.zul
@@ -72,7 +72,8 @@
                             <panel title="${i18n:_('Materials')}"
                                 border="normal">
                                 <panelchildren>
-                                    <button label="${i18n:_('Add')}"
+                                    <button id="btnAddMaterial"
+                                        label="${i18n:_('Add')}"
                                         onClick="materialsController.addMaterialToMaterialCategory(categoriesTree.selectedItem)" />
                                     <separator spacing="15px" orient="horizontal" />
                                     <newdatasortablegrid id="gridMaterials"