diff --git a/src/backend/InvenTree/InvenTree/serializers.py b/src/backend/InvenTree/InvenTree/serializers.py
index 1d4bbaaab0..d0d32b83d3 100644
--- a/src/backend/InvenTree/InvenTree/serializers.py
+++ b/src/backend/InvenTree/InvenTree/serializers.py
@@ -756,6 +756,9 @@ class ContentTypeField(serializers.ChoiceField):
                 (f'{ct.app_label}.{ct.model}', str(ct)) for ct in content_types
             ]
 
+        if kwargs.get('allow_null') or kwargs.get('allow_blank'):
+            kwargs['choices'] = [('', '---------'), *kwargs['choices']]
+
         super().__init__(*args, **kwargs)
 
     def to_representation(self, value):
diff --git a/src/backend/InvenTree/InvenTree/setting/spectacular.py b/src/backend/InvenTree/InvenTree/setting/spectacular.py
index 810e0a04e9..5591b86be7 100644
--- a/src/backend/InvenTree/InvenTree/setting/spectacular.py
+++ b/src/backend/InvenTree/InvenTree/setting/spectacular.py
@@ -29,6 +29,7 @@ def get_spectacular_settings():
             'TemplateModelTypeEnum': 'report.models.ReportTemplateBase.ModelChoices',
             'AttachmentModelTypeEnum': 'common.models.Attachment.ModelChoices',
             'ParameterModelTypeEnum': 'common.models.Parameter.ModelChoices',
+            'ParameterTemplateModelTypeEnum': 'common.models.ParameterTemplate.ModelChoices',
             'DataImportSessionModelTypeEnum': 'importer.models.DataImportSession.ModelChoices',
             # Allauth
             'UnauthorizedStatus': [[401, 401]],