diff --git a/src/writerai/resources/files.py b/src/writerai/resources/files.py
index 336ce0a..6af9b5b 100644
--- a/src/writerai/resources/files.py
+++ b/src/writerai/resources/files.py
@@ -211,7 +211,6 @@ def upload(
         *,
         content: FileTypes,
         content_disposition: str,
-        content_type: str,
         # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
         # The extra values given here take precedence over values defined on the client or passed to this method.
         extra_headers: Headers | None = None,
@@ -231,11 +230,7 @@ def upload(
 
           timeout: Override the client-level default timeout for this request, in seconds
         """
-        extra_headers = {
-            "Content-Disposition": content_disposition,
-            "Content-Type": content_type,
-            **(extra_headers or {}),
-        }
+        extra_headers = {"Content-Disposition": content_disposition, **(extra_headers or {})}
         return self._post(
             "/v1/files",
             options=make_request_options(
@@ -424,7 +419,6 @@ async def upload(
         *,
         content: FileTypes,
         content_disposition: str,
-        content_type: str,
         # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
         # The extra values given here take precedence over values defined on the client or passed to this method.
         extra_headers: Headers | None = None,
@@ -444,11 +438,7 @@ async def upload(
 
           timeout: Override the client-level default timeout for this request, in seconds
         """
-        extra_headers = {
-            "Content-Disposition": content_disposition,
-            "Content-Type": content_type,
-            **(extra_headers or {}),
-        }
+        extra_headers = {"Content-Disposition": content_disposition, **(extra_headers or {})}
         return await self._post(
             "/v1/files",
             options=make_request_options(
diff --git a/src/writerai/types/file_upload_params.py b/src/writerai/types/file_upload_params.py
index 14077b9..760021f 100644
--- a/src/writerai/types/file_upload_params.py
+++ b/src/writerai/types/file_upload_params.py
@@ -14,5 +14,3 @@ class FileUploadParams(TypedDict, total=False):
     content: Required[FileTypes]
 
     content_disposition: Required[Annotated[str, PropertyInfo(alias="Content-Disposition")]]
-
-    content_type: Required[Annotated[str, PropertyInfo(alias="Content-Type")]]
diff --git a/tests/api_resources/test_files.py b/tests/api_resources/test_files.py
index 6e02268..85041dc 100644
--- a/tests/api_resources/test_files.py
+++ b/tests/api_resources/test_files.py
@@ -198,7 +198,6 @@ def test_method_upload(self, client: Writer) -> None:
         file = client.files.upload(
             content=b"raw file contents",
             content_disposition="Content-Disposition",
-            content_type="Content-Type",
         )
         assert_matches_type(File, file, path=["response"])
 
@@ -208,7 +207,6 @@ def test_raw_response_upload(self, client: Writer) -> None:
         response = client.files.with_raw_response.upload(
             content=b"raw file contents",
             content_disposition="Content-Disposition",
-            content_type="Content-Type",
         )
 
         assert response.is_closed is True
@@ -222,7 +220,6 @@ def test_streaming_response_upload(self, client: Writer) -> None:
         with client.files.with_streaming_response.upload(
             content=b"raw file contents",
             content_disposition="Content-Disposition",
-            content_type="Content-Type",
         ) as response:
             assert not response.is_closed
             assert response.http_request.headers.get("X-Stainless-Lang") == "python"
@@ -408,7 +405,6 @@ async def test_method_upload(self, async_client: AsyncWriter) -> None:
         file = await async_client.files.upload(
             content=b"raw file contents",
             content_disposition="Content-Disposition",
-            content_type="Content-Type",
         )
         assert_matches_type(File, file, path=["response"])
 
@@ -418,7 +414,6 @@ async def test_raw_response_upload(self, async_client: AsyncWriter) -> None:
         response = await async_client.files.with_raw_response.upload(
             content=b"raw file contents",
             content_disposition="Content-Disposition",
-            content_type="Content-Type",
         )
 
         assert response.is_closed is True
@@ -432,7 +427,6 @@ async def test_streaming_response_upload(self, async_client: AsyncWriter) -> Non
         async with async_client.files.with_streaming_response.upload(
             content=b"raw file contents",
             content_disposition="Content-Disposition",
-            content_type="Content-Type",
         ) as response:
             assert not response.is_closed
             assert response.http_request.headers.get("X-Stainless-Lang") == "python"