diff --git a/pyinstrument/renderers/html.py b/pyinstrument/renderers/html.py
index e229a8c0..6e5839e8 100644
--- a/pyinstrument/renderers/html.py
+++ b/pyinstrument/renderers/html.py
@@ -41,8 +41,8 @@ def render(self, session: Session):
                 "Could not find app.js / app.css. Perhaps you need to run bin/build_js_bundle.py?"
             )
 
-        js = js_file.read_text(encoding='utf-8')
-        css = css_file.read_text(encoding='utf-8')
+        js = js_file.read_text(encoding="utf-8")
+        css = css_file.read_text(encoding="utf-8")
 
         session_json = self.render_json(session)