diff --git a/cps/opds.py b/cps/opds.py
index 329a6a0e5..0bd6756ff 100644
--- a/cps/opds.py
+++ b/cps/opds.py
@@ -440,7 +440,7 @@ def feed_shelf(book_id):
 def opds_download_link(book_id, book_format):
     if not auth.current_user().role_download():
         return abort(401)
-    client = "kobo" if "Kobo" in request.headers.get('User-Agent') else ""
+    client = request.headers.get('User-Agent', "").lower()
     return get_download_link(book_id, book_format.lower(), client)
 
 
diff --git a/cps/web.py b/cps/web.py
index 092c7f368..340df6fa5 100644
--- a/cps/web.py
+++ b/cps/web.py
@@ -1247,9 +1247,9 @@ def serve_book(book_id, book_format, anyname):
 @login_required_if_no_ano
 @download_required
 def download_link(book_id, book_format, anyname):
-    if "kindle" in request.headers.get('User-Agent').lower():
+    if "kindle" in request.headers.get('User-Agent', "").lower():
         client = "kindle"
-    elif "Kobo" in request.headers.get('User-Agent').lower():
+    elif "Kobo" in request.headers.get('User-Agent', "").lower():
         client = "kobo"
     else:
         client = ""