diff --git a/lib/Doctrine/ORM/ORMInvalidArgumentException.php b/lib/Doctrine/ORM/ORMInvalidArgumentException.php
index b4edc5dd2..a4a03c41a 100644
--- a/lib/Doctrine/ORM/ORMInvalidArgumentException.php
+++ b/lib/Doctrine/ORM/ORMInvalidArgumentException.php
@@ -68,6 +68,12 @@ class ORMInvalidArgumentException extends \InvalidArgumentException
                         . "during cascading a persist operation.");
     }
 
+    static public function entityNotManaged($entity)
+    {
+        throw new self("Entity " . self::objToStr($entity) . " is not managed. An entity is managed if its fetched " .
+                "from the database or registered as new through EntityManager#persist");
+    }
+
     /**
      * Helper method to show an object as string.
      *
diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 2b696063f..a80079041 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -653,7 +653,7 @@ class UnitOfWork implements PropertyChangedListener
         $oid = spl_object_hash($entity);
         
         if ( ! isset($this->entityStates[$oid]) || $this->entityStates[$oid] != self::STATE_MANAGED) {
-            throw new InvalidArgumentException("Entity of type '" . $class->name . "' must be managed.");
+            throw ORMInvalidArgumentException::entityNotManaged($entity);
         }
         
         /* TODO: Just return if changetracking policy is NOTIFY?
@@ -935,10 +935,10 @@ class UnitOfWork implements PropertyChangedListener
     {
         $oid = spl_object_hash($entity);
         if ( ! isset($this->entityIdentifiers[$oid])) {
-            throw new InvalidArgumentException("Entity has no identity.");
+            throw new InvalidArgumentException("Entity has no identity." . self::objToStr($entity));
         }
         if (isset($this->entityDeletions[$oid])) {
-            throw new InvalidArgumentException("Entity is removed.");
+            throw new InvalidArgumentException("Entity is removed." . self::objToStr($entity));
         }
 
         if ( ! isset($this->entityUpdates[$oid]) && ! isset($this->entityInsertions[$oid])) {
@@ -1160,7 +1160,7 @@ class UnitOfWork implements PropertyChangedListener
         $classMetadata = $this->em->getClassMetadata(get_class($entity));
         $idHash = implode(' ', $this->entityIdentifiers[$oid]);
         if ($idHash === '') {
-            throw new InvalidArgumentException("The given entity has no identity.");
+            throw new InvalidArgumentException("The given entity has no identity." . self::objToStr($entity));
         }
         $className = $classMetadata->rootEntityName;
         if (isset($this->identityMap[$className][$idHash])) {
@@ -1291,9 +1291,9 @@ class UnitOfWork implements PropertyChangedListener
                 break;
             case self::STATE_DETACHED:
                 // Can actually not happen right now since we assume STATE_NEW.
-                throw new InvalidArgumentException("Detached entity passed to persist().");
+                throw new InvalidArgumentException("Detached entity passed to persist()." . self::objToStr($entity));
             default:
-                throw new UnexpectedValueException("Unexpected entity state: $entityState.");
+                throw new UnexpectedValueException("Unexpected entity state: $entityState." . self::objToStr($entity));
         }
 
         $this->cascadePersist($entity, $visited);
@@ -1350,9 +1350,9 @@ class UnitOfWork implements PropertyChangedListener
                 $this->scheduleForDelete($entity);
                 break;
             case self::STATE_DETACHED:
-                throw new InvalidArgumentException("A detached entity can not be removed.");
+                throw new InvalidArgumentException("A detached entity can not be removed." . self::objToStr($entity));
             default:
-                throw new UnexpectedValueException("Unexpected entity state: $entityState.");
+                throw new UnexpectedValueException("Unexpected entity state: $entityState." . self::objToStr($entity));
         }
 
     }
@@ -1417,7 +1417,8 @@ class UnitOfWork implements PropertyChangedListener
                 if ($managedCopy) {
                     // We have the entity in-memory already, just make sure its not removed.
                     if ($this->getEntityState($managedCopy) == self::STATE_REMOVED) {
-                        throw new InvalidArgumentException('Removed entity detected during merge.'
+                        throw new InvalidArgumentException(
+                                'Removed entity ' . self::objToStr($managedCopy) . ' detected during merge.'
                                 . ' Can not merge with a removed entity.');
                     }
                 } else {
@@ -1624,7 +1625,7 @@ class UnitOfWork implements PropertyChangedListener
                 $entity
             );
         } else {
-            throw new InvalidArgumentException("Entity is not MANAGED.");
+            throw ORMInvalidArgumentException::entityNotManaged($entity);
         }
         
         $this->cascadeRefresh($entity, $visited);
@@ -1789,7 +1790,7 @@ class UnitOfWork implements PropertyChangedListener
     public function lock($entity, $lockMode, $lockVersion = null)
     {
         if ($this->getEntityState($entity, self::STATE_DETACHED) != self::STATE_MANAGED) {
-            throw new InvalidArgumentException("Entity is not MANAGED.");
+            throw ORMInvalidArgumentException::entityNotManaged($entity);
         }
         
         $entityName = get_class($entity);
diff --git a/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php b/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php
index 6917e7252..62c787409 100644
--- a/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php
+++ b/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php
@@ -71,7 +71,7 @@ class LockTest extends \Doctrine\Tests\OrmFunctionalTestCase {
     public function testLockUnmanagedEntity_ThrowsException() {
         $article = new CmsArticle();
 
-        $this->setExpectedException('InvalidArgumentException', 'Entity is not MANAGED.');
+        $this->setExpectedException('InvalidArgumentException', 'Entity Doctrine\Tests\Models\CMS\CmsArticle');
         $this->_em->lock($article, LockMode::OPTIMISTIC, $article->version + 1);
     }