diff --git a/product/ERP5Form/MultiRelationField.py b/product/ERP5Form/MultiRelationField.py
index d29ad3b5b4cb9b1a2a359b46f1983337f8401d99..96bef60c1216ac1bd2659e6d0a44ab789079b9c6 100755
--- a/product/ERP5Form/MultiRelationField.py
+++ b/product/ERP5Form/MultiRelationField.py
@@ -126,6 +126,7 @@ MultiRelationStringFieldValidatorInstance = Validator.LinesValidator()
 
 class MultiRelationStringField(ZMIField):
     meta_type = "MultiRelationStringField"
+    is_relation_field = 1
 
     widget = MultiRelationStringFieldWidgetInstance
     validator = MultiRelationStringFieldValidatorInstance