diff --git a/doc/en/conf.py b/doc/en/conf.py
index 90b41d023..aa2c54d93 100644
--- a/doc/en/conf.py
+++ b/doc/en/conf.py
@@ -62,7 +62,7 @@ extensions = [
 # conversion. The relevant plugin is not useful for normal HTML builds, but
 # it still raises warnings and fails CI if inkscape is not available. So
 # only use the plugin if inkscape is actually available.
-if shutil.which('inkscape'):
+if shutil.which("inkscape"):
     extensions.append("sphinxcontrib.inkscapeconverter")
 
 # Add any paths that contain templates here, relative to this directory.