diff --git a/fs_attachment/models/ir_attachment.py b/fs_attachment/models/ir_attachment.py
index 3379ab721d..d06ba1a90c 100644
--- a/fs_attachment/models/ir_attachment.py
+++ b/fs_attachment/models/ir_attachment.py
@@ -237,7 +237,9 @@ def _get_datas_related_values(self, data, mimetype):
                     "db_datas": data,
                 }
                 return values
-        return super()._get_datas_related_values(data, mimetype)
+        return super(
+            IrAttachment, self.with_context(mimetype=mimetype)
+        )._get_datas_related_values(data, mimetype)
 
     ###########################################################
     # Odoo methods that we override to use the object storage #
@@ -377,6 +379,14 @@ def _storage_file_read(self, fname: str) -> bytes | None:
             )
         return b""
 
+    def _storage_write_option(self, fs):
+        _fs = fs
+        while _fs:
+            if hasattr(_fs, "s3"):
+                return {"ContentType": self._context["mimetype"]}
+            _fs = getattr(_fs, "fs", None)
+        return {}
+
     @api.model
     def _storage_file_write(self, bin_data: bytes) -> str:
         """Write the file to the filesystem storage"""
@@ -387,7 +397,8 @@ def _storage_file_write(self, bin_data: bytes) -> str:
         if not fs.exists(dirname):
             fs.makedirs(dirname)
         fname = f"{storage}://{path}"
-        with fs.open(path, "wb") as f:
+        kwargs = self._storage_write_option(fs)
+        with fs.open(path, "wb", **kwargs) as f:
             f.write(bin_data)
         self._fs_mark_for_gc(fname)
         return fname