diff --git a/tljh/conda.py b/tljh/conda.py
index 1dbeb55..1ffe7ff 100644
--- a/tljh/conda.py
+++ b/tljh/conda.py
@@ -51,8 +51,10 @@ def download_miniconda_installer(installer_url, sha256sum):
     """
     with tempfile.NamedTemporaryFile('wb') as f:
         f.write(requests.get(installer_url).content)
+        # Remain in the NamedTemporaryFile context, but flush changes, see:
+        # https://docs.python.org/3/library/os.html#os.fsync
         f.flush()
-        os.fsync(f)
+        os.fsync(f.fileno())
 
         if sha256_file(f.name) != sha256sum:
             raise Exception('sha256sum hash mismatch! Downloaded file corrupted')