diff --git a/modules/api/models.py b/modules/api/models.py
index b568307141fd6945b7494dfde45ee8bf15aab219..b55fa72880f58263369c298cc59c4bf7b819a5bc 100644
--- a/modules/api/models.py
+++ b/modules/api/models.py
@@ -1,4 +1,6 @@
 import inspect
+import types
+
 from pydantic import BaseModel, Field, create_model
 from typing import Any, Optional
 from typing_extensions import Literal
@@ -207,11 +209,14 @@ class PreprocessResponse(BaseModel):
 fields = {}
 for key, metadata in opts.data_labels.items():
     value = opts.data.get(key)
+    if key == 'sd_model_checkpoint':
+        value = None
     optType = opts.typemap.get(type(metadata.default), type(value))
 
-    if (metadata is not None):
-        fields.update({key: (Optional[optType], Field(
-            default=metadata.default ,description=metadata.label))})
+    if optType == types.NoneType:
+        pass
+    elif metadata is not None:
+        fields.update({key: (Optional[optType], Field(default=metadata.default, description=metadata.label))})
     else:
         fields.update({key: (Optional[optType], Field())})