diff --git a/README.md b/README.md
index e4c329a..7671cb2 100644
--- a/README.md
+++ b/README.md
@@ -61,16 +61,16 @@ if res.task_id:
 ### Upload
 
 ```python
-from altertable_lakehouse.models import UploadFormat, UploadMode
+from altertable_lakehouse.models import UploadMode
 
 with open("data.csv", "rb") as f:
     client.upload(
         catalog="my_cat", 
         schema="my_schema", 
         table="my_table", 
-        format=UploadFormat.CSV, 
         mode=UploadMode.APPEND, 
-        content=f.read()
+        content=f.read(),
+        content_type="text/csv"
     )
 ```
 
diff --git a/src/altertable_lakehouse/client.py b/src/altertable_lakehouse/client.py
index 1a5aed4..b1876d8 100644
--- a/src/altertable_lakehouse/client.py
+++ b/src/altertable_lakehouse/client.py
@@ -16,7 +16,6 @@
     ValidateResponse,
     AutocompleteRequest,
     AutocompleteResponse,
-    UploadFormat,
     UploadMode,
     QueryMetadata,
     QueryResult,
@@ -124,26 +123,26 @@ def upload(
         catalog: str,
         schema: str,
         table: str,
-        format: UploadFormat,
-        mode: UploadMode,
         content: bytes,
+        mode: Optional[UploadMode] = None,
         primary_key: Optional[str] = None,
+        content_type: str = "application/octet-stream",
     ) -> None:
         params = {
             "catalog": catalog,
             "schema": schema,
             "table": table,
-            "format": format.value,
-            "mode": mode.value,
         }
+        if mode is not None:
+            params["mode"] = mode.value
         if primary_key:
             params["primary_key"] = primary_key
         try:
             res = self._client.post(
-                "/upload",
+                "/upsert",
                 params=params,
                 content=content,
-                headers={"Content-Type": "application/octet-stream"},
+                headers={"Content-Type": content_type},
             )
             self._check_response(res)
         except httpx.RequestError as e:
diff --git a/src/altertable_lakehouse/models.py b/src/altertable_lakehouse/models.py
index d69725e..fced3e3 100644
--- a/src/altertable_lakehouse/models.py
+++ b/src/altertable_lakehouse/models.py
@@ -11,12 +11,6 @@ class ComputeSize(str, Enum):
     XL = "XL"
 
 
-class UploadFormat(str, Enum):
-    CSV = "csv"
-    JSON = "json"
-    PARQUET = "parquet"
-
-
 class UploadMode(str, Enum):
     CREATE = "create"
     APPEND = "append"
diff --git a/tests/test_client.py b/tests/test_client.py
index f59c404..00157af 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -47,7 +47,7 @@ def test_query_all(client):
 
 def test_upload(client):
     try:
-        client.upload(catalog="cat", schema="sch", table="tbl", format=models.UploadFormat.JSON, mode=models.UploadMode.APPEND, content=b'{"a":1}')
+        client.upload(catalog="cat", schema="sch", table="tbl", mode=models.UploadMode.APPEND, content=b'{"a":1}', content_type="application/json")
     except errors.BadRequestError:
         pass