diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 0ebdedcb9..6142ca958 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -707,6 +707,15 @@ class UnitOfWork implements PropertyChangedListener
             $state = $this->getEntityState($entry, self::STATE_NEW);
             $oid   = spl_object_hash($entry);
 
+            if (!($entry instanceof $assoc['targetEntity'])) {
+                throw new ORMException(sprintf("Found entity of type %s on association %s#%s, but expecting %s",
+                    get_class($entry),
+                    $assoc['sourceEntity'],
+                    $assoc['fieldName'],
+                    $targetClass->name
+                ));
+            }
+
             switch ($state) {
                 case self::STATE_NEW:
                     if ( ! $assoc['isCascadePersist']) {
diff --git a/tests/Doctrine/Tests/ORM/Functional/BasicFunctionalTest.php b/tests/Doctrine/Tests/ORM/Functional/BasicFunctionalTest.php
index 9b68098c0..3955387e0 100644
--- a/tests/Doctrine/Tests/ORM/Functional/BasicFunctionalTest.php
+++ b/tests/Doctrine/Tests/ORM/Functional/BasicFunctionalTest.php
@@ -1197,4 +1197,21 @@ class BasicFunctionalTest extends \Doctrine\Tests\OrmFunctionalTestCase
         $user2 = $this->_em->find(get_class($user2), $user2->id);
         $this->assertEquals('developer', $user2->status);
     }
+
+    /**
+     * @group DDC-1585
+     */
+    public function testWrongAssocationInstance()
+    {
+        $user = new CmsUser;
+        $user->name = 'Dominik';
+        $user->username = 'domnikl';
+        $user->status = 'developer';
+        $user->address = $user;
+
+        $this->_em->persist($user);
+
+        $this->setExpectedException("Doctrine\ORM\ORMException", "Found entity of type Doctrine\Tests\Models\CMS\CmsUser on association Doctrine\Tests\Models\CMS\CmsUser#address, but expecting Doctrine\Tests\Models\CMS\CmsAddress");
+        $this->_em->flush();
+    }
 }