diff --git a/odoo/models.py b/odoo/models.py
index 783a3b09cff..ce1b41d4134 100644
--- a/odoo/models.py
+++ b/odoo/models.py
@@ -2728,6 +2728,17 @@ class BaseModel(metaclass=MetaModel):
                 for field in klass._field_definitions:
                     definitions[field.name].append(field)
         for name, fields_ in definitions.items():
+            if f'{cls._name}.{name}' in cls.pool._database_translated_fields:
+                # the field is currently translated in the database; ensure the
+                # field is translated to avoid converting its column to varchar
+                # and losing data
+                translate = next((
+                    field.args['translate'] for field in reversed(fields_) if 'translate' in field.args
+                ), False)
+                if not translate:
+                    # patch the field definition by adding an override
+                    _logger.debug("Patching %s.%s with translate=True", cls._name, name)
+                    fields_.append(fields_[0].new(translate=True))
             if len(fields_) == 1 and fields_[0]._direct and fields_[0].model_name == cls._name:
                 cls._fields[name] = fields_[0]
             else:
diff --git a/odoo/modules/loading.py b/odoo/modules/loading.py
index 33b1a69fba9..e805a1781ab 100644
--- a/odoo/modules/loading.py
+++ b/odoo/modules/loading.py
@@ -411,6 +411,11 @@ def load_modules(registry, force_demo=False, status=None, update_module=False):
             _logger.critical('module base cannot be loaded! (hint: verify addons-path)')
             raise ImportError('Module `base` cannot be loaded! (hint: verify addons-path)')
 
+        if update_module and odoo.tools.table_exists(cr, 'ir_model_fields'):
+            # determine the fields which are currently translated in the database
+            cr.execute("SELECT model || '.' || name FROM ir_model_fields WHERE translate IS TRUE")
+            registry._database_translated_fields = {row[0] for row in cr.fetchall()}
+
         # processed_modules: for cleanup step after install
         # loaded_modules: to avoid double loading
         report = registry._assertion_report
@@ -477,6 +482,23 @@ def load_modules(registry, force_demo=False, status=None, update_module=False):
                     ['to install'], force, status, report,
                     loaded_modules, update_module, models_to_check)
 
+        if update_module:
+            # set up the registry without the patch for translated fields
+            database_translated_fields = registry._database_translated_fields
+            registry._database_translated_fields = ()
+            registry.setup_models(cr)
+            # determine which translated fields should no longer be translated,
+            # and make their model fix the database schema
+            models_to_untranslate = set()
+            for full_name in database_translated_fields:
+                model_name, field_name = full_name.rsplit('.', 1)
+                if model_name in registry:
+                    field = registry[model_name]._fields.get(field_name)
+                    if field and not field.translate:
+                        _logger.debug("Making field %s non-translated", field)
+                        models_to_untranslate.add(model_name)
+            registry.init_models(cr, list(models_to_untranslate), {'models_to_check': True})
+
         registry.loaded = True
         registry.setup_models(cr)
 
diff --git a/odoo/modules/registry.py b/odoo/modules/registry.py
index be0cc51b3bd..61e5da4973c 100644
--- a/odoo/modules/registry.py
+++ b/odoo/modules/registry.py
@@ -113,6 +113,7 @@ class Registry(Mapping):
         self.models = {}    # model name/model instance mapping
         self._sql_constraints = set()
         self._init = True
+        self._database_translated_fields = ()  # names of translated fields in database
         self._assertion_report = odoo.tests.runner.OdooTestResult()
         self._fields_by_model = None
         self._ordinary_tables = None