diff --git a/lib/Doctrine/ORM/Id/AssignedGenerator.php b/lib/Doctrine/ORM/Id/AssignedGenerator.php
index 05c3790af..90a35fa12 100644
--- a/lib/Doctrine/ORM/Id/AssignedGenerator.php
+++ b/lib/Doctrine/ORM/Id/AssignedGenerator.php
@@ -53,14 +53,14 @@ class AssignedGenerator extends AbstractIdGenerator
                         if (!$em->getUnitOfWork()->isInIdentityMap($value)) {
                             throw ORMException::entityMissingForeignAssignedId($entity, $value);
                         }
-                        
+
                         // NOTE: Single Columns as associated identifiers only allowed - this constraint it is enforced.
                         $identifier[$idField] = current($em->getUnitOfWork()->getEntityIdentifier($value));
                     } else {
                         $identifier[$idField] = $value;
                     }
                 } else {
-                    throw ORMException::entityMissingAssignedId($entity);
+                    throw ORMException::entityMissingAssignedIdForField($entity, $idField);
                 }
             }
         } else {
@@ -71,17 +71,17 @@ class AssignedGenerator extends AbstractIdGenerator
                     if (!$em->getUnitOfWork()->isInIdentityMap($value)) {
                         throw ORMException::entityMissingForeignAssignedId($entity, $value);
                     }
-                    
+
                     // NOTE: Single Columns as associated identifiers only allowed - this constraint it is enforced.
                     $identifier[$idField] = current($em->getUnitOfWork()->getEntityIdentifier($value));
                 } else {
                     $identifier[$idField] = $value;
                 }
             } else {
-                throw ORMException::entityMissingAssignedId($entity);
+                throw ORMException::entityMissingAssignedIdForField($entity, $idField);
             }
         }
-        
+
         return $identifier;
     }
-}
\ No newline at end of file
+}
diff --git a/lib/Doctrine/ORM/ORMException.php b/lib/Doctrine/ORM/ORMException.php
index aa9657552..c156893c5 100644
--- a/lib/Doctrine/ORM/ORMException.php
+++ b/lib/Doctrine/ORM/ORMException.php
@@ -34,7 +34,7 @@ class ORMException extends Exception
         return new self("It's a requirement to specify a Metadata Driver and pass it ".
             "to Doctrine\ORM\Configuration::setMetadataDriverImpl().");
     }
-    
+
     public static function entityMissingForeignAssignedId($entity, $relatedEntity)
     {
         return new self(
@@ -46,15 +46,14 @@ class ORMException extends Exception
         );
     }
 
-    public static function entityMissingAssignedId($entity)
+    public static function entityMissingAssignedIdForField($entity, $field)
     {
-        return new self("Entity of type " . get_class($entity) . " is missing an assigned ID. " .
+        return new self("Entity of type " . get_class($entity) . " is missing an assigned ID for field  '" . $field . "'. " .
             "The identifier generation strategy for this entity requires the ID field to be populated before ".
-            "EntityManager#persist() is called. If you want automatically generated identifiers instead " . 
+            "EntityManager#persist() is called. If you want automatically generated identifiers instead " .
             "you need to adjust the metadata mapping accordingly."
         );
     }
-
     public static function unrecognizedField($field)
     {
         return new self("Unrecognized field: $field");
@@ -130,8 +129,8 @@ class ORMException extends Exception
             "Unknown Entity namespace alias '$entityNamespaceAlias'."
         );
     }
-    
-    public static function invalidEntityRepository($className) 
+
+    public static function invalidEntityRepository($className)
     {
         return new self("Invalid repository class '".$className."'. ".
                 "it must be a Doctrine\ORM\EntityRepository.");