diff --git a/src/black/files.py b/src/black/files.py
index 4d7b47aaa9f..eb4a94a5e60 100644
--- a/src/black/files.py
+++ b/src/black/files.py
@@ -93,8 +93,8 @@ def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:
 
     If parsing fails, will raise a tomli.TOMLDecodeError
     """
-    with open(path_config, encoding="utf8") as f:
-        pyproject_toml = tomli.load(f)  # type: ignore  # due to deprecated API usage
+    with open(path_config, "rb") as f:
+        pyproject_toml = tomli.load(f)
     config = pyproject_toml.get("tool", {}).get("black", {})
     return {k.replace("--", "").replace("-", "_"): v for k, v in config.items()}