diff --git a/Cake/Database/Type.php b/Cake/Database/Type.php
index d5f62cbb771..0eb16486834 100644
--- a/Cake/Database/Type.php
+++ b/Cake/Database/Type.php
@@ -17,7 +17,6 @@
 namespace Cake\Database;
 
 use Cake\Database\Driver;
-use Exception;
 use PDO;
 
 /**
diff --git a/Cake/ORM/Association/BelongsToMany.php b/Cake/ORM/Association/BelongsToMany.php
index fce48ab25a9..2271e72e93f 100644
--- a/Cake/ORM/Association/BelongsToMany.php
+++ b/Cake/ORM/Association/BelongsToMany.php
@@ -484,8 +484,9 @@ public function replaceLinks(Entity $sourceEntity, array $targetEntities, array
 		$primaryKey = (array)$this->source()->primaryKey();
 		$primaryValue = $sourceEntity->extract($primaryKey);
 
-		if (empty($primaryValue)) {
-			throw new \InvalidArgumentException;
+		if (count(array_filter($primaryValue, 'strlen')) !== count($primaryKey)) {
+			$message = __d('cake_dev', 'Could not find primary key value for source entity');
+			throw new \InvalidArgumentException($message);
 		}
 
 		return $this->junction()->connection()->transactional(
diff --git a/Cake/Test/TestCase/ORM/Association/BelongsToManyTest.php b/Cake/Test/TestCase/ORM/Association/BelongsToManyTest.php
index 8d37712b71b..eaf1ddbea1b 100644
--- a/Cake/Test/TestCase/ORM/Association/BelongsToManyTest.php
+++ b/Cake/Test/TestCase/ORM/Association/BelongsToManyTest.php
@@ -899,4 +899,23 @@ public function testUnlinkWithoutPropertyClean() {
 		$this->assertEquals($tags, $entity->get('test'));
 	}
 
+/**
+ * Test liking entities having a non persited source entity
+ *
+ * @expectedException \InvalidArgumentException
+ * @expectedExceptionMessage Could not find primary key value for source entity
+ * @return void
+ */
+	public function testRplaceWithMissingPrimaryKey() {
+		$config = [
+			'sourceTable' => $this->article,
+			'targetTable' => $this->tag,
+			'joinTable' => 'tags_articles'
+		];
+		$assoc = new BelongsToMany('Test', $config);
+		$entity = new Entity(['foo' => 1], ['markNew' => false]);
+		$tags = [new Entity(['id' => 2]), new Entity(['id' => 3])];
+		$assoc->replaceLinks($entity, $tags);
+	}
+
 }