diff --git a/langfuse/api/resources/commons/types/model.py b/langfuse/api/resources/commons/types/model.py
index 18b26c478..54cb26bc8 100644
--- a/langfuse/api/resources/commons/types/model.py
+++ b/langfuse/api/resources/commons/types/model.py
@@ -24,14 +24,14 @@ class Model(pydantic_v1.BaseModel):
     Regex pattern which matches this model definition to generation.model. Useful in case of fine-tuned models. If you want to exact match, use `(?i)^modelname$`
     """
 
-    start_date: typing.Optional[dt.date] = pydantic_v1.Field(
+    start_date: typing.Optional[dt.datetime] = pydantic_v1.Field(
         alias="startDate", default=None
     )
     """
     Apply only to generations which are newer than this ISO date.
     """
 
-    unit: ModelUsageUnit = pydantic_v1.Field()
+    unit: typing.Optional[ModelUsageUnit] = pydantic_v1.Field(default=None)
     """
     Unit used by this model.
     """