diff --git a/src/Model/Behavior/DuplicatableBehavior.php b/src/Model/Behavior/DuplicatableBehavior.php
index bff439c..794aaf3 100644
--- a/src/Model/Behavior/DuplicatableBehavior.php
+++ b/src/Model/Behavior/DuplicatableBehavior.php
@@ -178,9 +178,9 @@ protected function _getContain()
     protected function _modifyEntity(EntityInterface $entity, $object)
     {
         // belongs to many is tricky
-        if ($object instanceof BelongsToMany && ! $this->getConfig('preserveJoinData')) {
+        if ($object instanceof BelongsToMany && !$this->getConfig('preserveJoinData')) {
             unset($entity->_joinData);
-        } else {
+        } elseif (!$object instanceof BelongsToMany) {
             // unset primary key
             unset($entity->{$object->getPrimaryKey()});
 
diff --git a/tests/TestCase/Model/Behavior/DuplicatableBehaviorTest.php b/tests/TestCase/Model/Behavior/DuplicatableBehaviorTest.php
index 3e22a71..88b9389 100644
--- a/tests/TestCase/Model/Behavior/DuplicatableBehaviorTest.php
+++ b/tests/TestCase/Model/Behavior/DuplicatableBehaviorTest.php
@@ -213,28 +213,20 @@ public function testPreserveJoinData()
             'contain' => [
                 'Tags',
             ],
-            'preserveJoinData' => false,
+            'preserveJoinData' => true,
         ]);
 
-        $duplicated = $this->Invoices->duplicateEntity(1);
-
-        $this->assertEquals(false, isset($duplicated->tags[0]->_joinData));
-        $this->assertEquals(false, isset($duplicated->tags[1]->_joinData));
-
-        $this->Invoices->removeBehavior('Duplicatable');
-
-        $this->Invoices->addBehavior('Duplicatable.Duplicatable', [
+        $result = $this->Invoices->duplicate(1);
+        $invoice = $this->Invoices->get($result->id, [
             'contain' => [
                 'Tags',
-            ],
-            'preserveJoinData' => true,
+            ]
         ]);
 
-        $duplicated = $this->Invoices->duplicateEntity(1);
+        $this->assertEquals(true, $invoice->tags[0]->_joinData->is_preserved);
+        $this->assertEquals(true, $invoice->tags[1]->_joinData->is_preserved);
 
-        $this->assertEquals(true, isset($duplicated->tags[0]->_joinData));
-        $this->assertEquals(true, isset($duplicated->tags[1]->_joinData));
-        $this->assertEquals(true, $duplicated->tags[0]->_joinData->is_preserved);
-        $this->assertEquals(true, $duplicated->tags[1]->_joinData->is_preserved);
+        // check that tags are not duplicated
+        $this->assertEquals(2, $this->Invoices->Tags->find()->count());
     }
 }