diff --git a/server/src/scimodom/services/file.py b/server/src/scimodom/services/file.py
index 9ea6a3b9..50109c31 100644
--- a/server/src/scimodom/services/file.py
+++ b/server/src/scimodom/services/file.py
@@ -379,7 +379,7 @@ def _stream_to_file(self, data_stream, path, max_size, overwrite_is_ok=False):
         self._create_folder(dirname(path))
         try:
             bytes_written = 0
-            with open(path, "wb", opener=write_opener()) as fp:
+            with open(path, "wb", opener=write_opener) as fp:
                 while True:
                     buffer = data_stream.read(self.BUFFER_SIZE)
                     if len(buffer) == 0: