diff --git a/modules/backend/behaviors/RelationController.php b/modules/backend/behaviors/RelationController.php
index a53fff7a5..8d14251e6 100644
--- a/modules/backend/behaviors/RelationController.php
+++ b/modules/backend/behaviors/RelationController.php
@@ -414,7 +414,7 @@ class RelationController extends ControllerBehavior
      */
     protected function findExistingRelationIds($checkIds = null)
     {
-        $foreignKeyName = $this->relationModel->getKeyName();
+        $foreignKeyName = $this->relationModel->table . '.' . $this->relationModel->getKeyName();
 
         $results = $this->relationObject
             ->getBaseQuery()
@@ -818,4 +818,4 @@ class RelationController extends ControllerBehavior
         return $this->sessionKey = FormHelper::getSessionKey();
     }
 
-}
\ No newline at end of file
+}