diff --git a/netbox/netbox/forms/base.py b/netbox/netbox/forms/base.py
index d59f61ef9b9..74ac4b0e005 100644
--- a/netbox/netbox/forms/base.py
+++ b/netbox/netbox/forms/base.py
@@ -60,6 +60,8 @@ def clean(self):
             if value in self.fields[cf_name].empty_values:
                 self.instance.custom_field_data[key] = None
             else:
+                if customfield.type == CustomFieldTypeChoices.TYPE_JSON and type(value) is str:
+                    value = json.loads(value)
                 self.instance.custom_field_data[key] = customfield.serialize(value)
 
         return super().clean()