diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java
index 449646afe..373495de1 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/Material.java
@@ -44,7 +44,7 @@ public class Material extends BaseEntity {
     private boolean disabled;
 
     @NotNull
-    private MaterialCategory category;
+    private MaterialCategory category = null;
 
     // Default constructor, needed by Hibernate
     protected Material() {
@@ -72,7 +72,10 @@ public class Material extends BaseEntity {
     }
 
     public void setCategory(MaterialCategory category) {
+        if(this.category!=null)
+            this.category.removeMaterial(this);
         this.category = category;
+        category.addMaterial(this);
     }
 
     public String getDescription() {
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialCategory.java b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialCategory.java
index 3b0e5e1c3..fd3ecbc91 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialCategory.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/materials/entities/MaterialCategory.java
@@ -97,4 +97,17 @@ public class MaterialCategory extends BaseEntity {
         if(subcategory.getParent()!=null)
             subcategory.removeParent();
     }
+
+    public Set<Material> getMaterials() {
+        return materials;
+    }
+
+    public void addMaterial(Material material) {
+        materials.add(material);
+        if(material.getCategory()!=this)
+            material.setCategory(this);
+    }
+    public void removeMaterial(Material material) {
+        materials.remove(material);
+    }
 }
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/materials/daos/MaterialDAOTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/materials/daos/MaterialDAOTest.java
index 55b9e1b1b..06a37f6a7 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/materials/daos/MaterialDAOTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/materials/daos/MaterialDAOTest.java
@@ -28,6 +28,7 @@ import static org.navalplanner.business.BusinessGlobalNames.BUSINESS_SPRING_CONF
 import static org.navalplanner.business.test.BusinessGlobalNames.BUSINESS_SPRING_CONFIG_TEST_FILE;
 
 import java.util.List;
+import java.util.Set;
 import java.util.UUID;
 
 import org.junit.Test;
@@ -84,6 +85,7 @@ public class MaterialDAOTest {
     public void testRemoveMaterial() throws InstanceNotFoundException {
         Material material = createValidMaterial();
         materialDAO.save(material);
+        //material.getCategory().removeMaterial(material);
         materialDAO.remove(material.getId());
         assertFalse(materialDAO.exists(material.getId()));
     }
@@ -96,4 +98,17 @@ public class MaterialDAOTest {
         List<Material> list = materialDAO.list(Material.class);
         assertEquals(previous + 1, list.size());
     }
+
+    @Test
+    public void testListMaterialsFromCategory() {
+        Material material1 = createValidMaterial();
+        int previous = material1.getCategory().getMaterials().size();
+        Material material2 = createValidMaterial();
+        material2.setCategory(material1.getCategory());
+        materialDAO.save(material1);
+        materialDAO.save(material2);
+
+        Set<Material> list = material1.getCategory().getMaterials();
+        assertEquals(previous + 1, list.size());
+    }
 }