diff --git a/mypy/config_parser.py b/mypy/config_parser.py
index d5552186ecc70..132a77cf94f46 100644
--- a/mypy/config_parser.py
+++ b/mypy/config_parser.py
@@ -168,7 +168,7 @@ def parse_config_file(options: Options, set_strict_flags: Callable[[], None],
             continue
         try:
             if is_toml(config_file):
-                with open(config_file, encoding="utf-8") as f:
+                with open(config_file, 'rb', encoding="utf-8") as f:
                     toml_data = tomli.load(f)
                 # Filter down to just mypy relevant toml keys
                 toml_data = toml_data.get('tool', {})
diff --git a/mypy/modulefinder.py b/mypy/modulefinder.py
index 6cebd7db8bc0b..1570a322a6802 100644
--- a/mypy/modulefinder.py
+++ b/mypy/modulefinder.py
@@ -434,7 +434,7 @@ def _is_compatible_stub_package(self, stub_dir: str) -> bool:
         if os.path.isfile(metadata_fnam):
             # Delay import for a possible minor performance win.
             import tomli
-            with open(metadata_fnam, 'r', encoding="utf-8") as f:
+            with open(metadata_fnam, 'rb', encoding="utf-8") as f:
                 metadata = tomli.load(f)
             if self.python_major_ver == 2:
                 return bool(metadata.get('python2', False))