diff --git a/application/Espo/ORM/DB/BaseMapper.php b/application/Espo/ORM/DB/BaseMapper.php
index 999e1d6bc9..fcbad2ea21 100644
--- a/application/Espo/ORM/DB/BaseMapper.php
+++ b/application/Espo/ORM/DB/BaseMapper.php
@@ -1207,9 +1207,4 @@ abstract class BaseMapper implements Mapper
     }
 
     abstract protected function toDb(string $attribute);
-
-    public function setCollectionClass(string $collectionClass)
-    {
-        $this->collectionClass = $collectionClass;
-    }
 }
diff --git a/application/Espo/ORM/DB/Mapper.php b/application/Espo/ORM/DB/Mapper.php
index e3384279bc..4e631665b0 100644
--- a/application/Espo/ORM/DB/Mapper.php
+++ b/application/Espo/ORM/DB/Mapper.php
@@ -142,11 +142,6 @@ interface Mapper
      */
     public function delete(Entity $entity) : bool;
 
-    /**
-     * Set a class name of a a model collection that will be returned by operations such as select.
-     */
-    public function setCollectionClass(string $collectionClass);
-
     /**
      * Delete a record from DB.
      */