diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Dependency.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Dependency.java
index 078a95e5b..d98a83e2b 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Dependency.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Dependency.java
@@ -1,5 +1,7 @@
 package org.navalplanner.business.planner.entities;
 
+import org.apache.commons.lang.Validate;
+
 /**
  * @author Óscar González Fernández <ogonzalez@igalia.com>
  */
@@ -29,9 +31,14 @@ public class Dependency {
     public Dependency() {
     }
 
-    private Dependency(TaskElement origin, TaskElement end, Type type) {
+    private Dependency(TaskElement origin, TaskElement destination, Type type) {
+        Validate.notNull(origin);
+        Validate.notNull(destination);
+        Validate.notNull(type);
+        Validate.isTrue(!origin.equals(destination),
+                "a dependency must have a different origin than destination");
         this.origin = origin;
-        this.destination = end;
+        this.destination = destination;
         this.type = type;
     }
 
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/DependencyTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/DependencyTest.java
index 8670640d8..4644defdb 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/DependencyTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/DependencyTest.java
@@ -4,6 +4,7 @@ import static org.hamcrest.CoreMatchers.equalTo;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import org.junit.Test;
 import org.navalplanner.business.planner.entities.Dependency;
@@ -41,6 +42,30 @@ public class DependencyTest {
         assertThat(dependency.getType(), equalTo(type));
     }
 
+    @Test
+    public void mustNotAllowANullValuesForAnyOfTheCreationArguments() {
+        Object[] arguments = { origin, destination, type };
+        for (int i = 0; i < arguments.length; i++) {
+            Object[] cloned = arguments.clone();
+            cloned[i] = null;
+            TaskElement origin = (TaskElement) cloned[0];
+            TaskElement destination = (TaskElement) cloned[1];
+            Type type = (Type) cloned[2];
+            try {
+                Dependency.createDependency(origin, destination, type);
+                fail("must send IllegalArgumentException");
+            } catch (IllegalArgumentException e) {
+                // ok
+            }
+        }
+
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void dependencyMustNotAllowTheSameOriginAndDestination() {
+        Dependency.createDependency(origin, origin, type);
+    }
+
     @Test
     public void creatingDependencyImpliesAssociatingItWithTheRelatedTasks() {
         assertFalse(origin.getDependenciesWithThisDestination().contains(