diff --git a/yt_dlp/extractor/cbc.py b/yt_dlp/extractor/cbc.py
index 33299e9404..ac1272f7b5 100644
--- a/yt_dlp/extractor/cbc.py
+++ b/yt_dlp/extractor/cbc.py
@@ -340,7 +340,8 @@ def _find_secret_formats(self, formats, video_id):
                 yield {
                     **base_format,
                     'format_id': join_nonempty('sec', height),
-                    'url': re.sub(r'(QualityLevels\()\d+(\))', fr'\1{bitrate}\2', base_url),
+                    # Note: \g<1> is necessary instead of \1 since bitrate is a number
+                    'url': re.sub(r'(QualityLevels\()\d+(\))', fr'\g<1>{bitrate}\2', base_url),
                     'width': int_or_none(video_quality.attrib.get('MaxWidth')),
                     'tbr': bitrate / 1000.0,
                     'height': height,