diff --git a/src/Rel/BelongsTo.php b/src/Rel/BelongsTo.php
index 3862213..152f2e7 100644
--- a/src/Rel/BelongsTo.php
+++ b/src/Rel/BelongsTo.php
@@ -53,7 +53,7 @@ public function getKey()
      */
     public function getForeignKey()
     {
-        return $this->getConfig()->getPrimaryKey();
+        return $this->getRepo()->getConfig()->getPrimaryKey();
     }
 
     /**