diff --git a/openupgradelib/openupgrade_120.py b/openupgradelib/openupgrade_120.py
index <HASH>..<HASH> 100644
--- a/openupgradelib/openupgrade_120.py
+++ b/openupgradelib/openupgrade_120.py
@@ -362,7 +362,7 @@ def _convert_field_bootstrap_3to4_orm(env, model_name, field_name,
     update_field_multilang(
         records,
         field_name,
-        lambda old, *a, **k: convert_field_bootstrap_3to4(old),
+        lambda old, *a, **k: convert_string_bootstrap_3to4(old),
     )
[FIX] typo in <I> tools

Fix typo in openupgrade_<I> in `_convert_field_bootstrap_3to4_orm` method. it have to call string conversion.