diff --git a/src/microcosm/__init__.py b/src/microcosm/__init__.py
index 733e9b1..1e35f22 100644
--- a/src/microcosm/__init__.py
+++ b/src/microcosm/__init__.py
@@ -7,6 +7,7 @@ import giteapy
 import giteapy.rest
 import time
 import base64
+import mimetypes
 
 
 from werkzeug.datastructures import FileStorage
@@ -143,8 +144,13 @@ def process_photo_upload(created_at: datetime, file: FileStorage, suffix: str=""
 
     if os.environ.get('MICROPUB_IMAGE_STRATEGY') == 'copy':
 
+        file.mimetype
+
         ext = os.path.splitext(file.filename)[1]
 
+        if ext == "":
+            ext = mimetypes.guess_extension(file.mimetype)
+
         # generate local filename
         filename = os.path.join(os.environ.get(
             'MICROPUB_MEDIA_PATH'), created_at.strftime("%Y/%m/%d"), f"{now_ts}_{suffix}{ext}")