From 465415989922c33faeb23a9533bfda9ec03ce1be Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 31 Jul 2022 21:24:06 +0530
Subject: [PATCH] Workaround for css-parser not serializing @supports rules
 correctly

---
 src/calibre/ebooks/oeb/polish/utils.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/calibre/ebooks/oeb/polish/utils.py b/src/calibre/ebooks/oeb/polish/utils.py
index d27626541d..d2dd7e916d 100644
--- a/src/calibre/ebooks/oeb/polish/utils.py
+++ b/src/calibre/ebooks/oeb/polish/utils.py
@@ -77,6 +77,7 @@ def setup_css_parser_serialization(tab_width=2):
     prefs.indent = tab_width * ' '
     prefs.indentClosingBrace = False
     prefs.omitLastSemicolon = False
+    prefs.formatUnknownAtRules = False  # True breaks @supports rules
 
 
 def actual_case_for_name(container, name):