diff --git a/isort/place.py b/isort/place.py
index aaf954aa8..47a68c78a 100644
--- a/isort/place.py
+++ b/isort/place.py
@@ -125,14 +125,14 @@ def _is_namespace_package(path: Path, src_extensions: FrozenSet[str]) -> bool:
         if filenames:
             return False
     else:
-        with init_file.open() as open_init_file:
+        with init_file.open("rb") as open_init_file:
             file_start = open_init_file.read(4096)
             if (
-                "__import__('pkg_resources').declare_namespace(__name__)" not in file_start
-                and '__import__("pkg_resources").declare_namespace(__name__)' not in file_start
-                and "__path__ = __import__('pkgutil').extend_path(__path__, __name__)"
+                b"__import__('pkg_resources').declare_namespace(__name__)" not in file_start
+                and b'__import__("pkg_resources").declare_namespace(__name__)' not in file_start
+                and b"__path__ = __import__('pkgutil').extend_path(__path__, __name__)"
                 not in file_start
-                and '__path__ = __import__("pkgutil").extend_path(__path__, __name__)'
+                and b'__path__ = __import__("pkgutil").extend_path(__path__, __name__)'
                 not in file_start
             ):
                 return False
diff --git a/tests/unit/example_projects/namespaces/weird_encoding/.isort.cfg b/tests/unit/example_projects/namespaces/weird_encoding/.isort.cfg
new file mode 100644
index 000000000..d3ae4c35a
--- /dev/null
+++ b/tests/unit/example_projects/namespaces/weird_encoding/.isort.cfg
@@ -0,0 +1,2 @@
+[settings]
+src_paths=root
diff --git a/tests/unit/example_projects/namespaces/weird_encoding/root/__init__.py b/tests/unit/example_projects/namespaces/weird_encoding/root/__init__.py
new file mode 100644
index 000000000..1b8a961c7
--- /dev/null
+++ b/tests/unit/example_projects/namespaces/weird_encoding/root/__init__.py
@@ -0,0 +1 @@
+description = "基于FastAPI + Mysql的 TodoList"  # Exception: UnicodeDecodeError
diff --git a/tests/unit/example_projects/namespaces/weird_encoding/root/nested/__init__.py b/tests/unit/example_projects/namespaces/weird_encoding/root/nested/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/unit/test_place.py b/tests/unit/test_place.py
index 18ac7fccd..11abdd66e 100644
--- a/tests/unit/test_place.py
+++ b/tests/unit/test_place.py
@@ -47,7 +47,8 @@ def test_namespace_package_placement(examples_path):
 
     no_namespace = namespace_examples / "none"
     almost_implicit = namespace_examples / "almost-implicit"
-    for lacks_namespace in (no_namespace, almost_implicit):
+    weird_encoding = namespace_examples / "weird_encoding"
+    for lacks_namespace in (no_namespace, almost_implicit, weird_encoding):
         config = Config(settings_path=lacks_namespace)
         manual_namespace = Config(settings_path=lacks_namespace, namespace_packages=["root"])
         assert place.module("root.name", config=config) == "FIRSTPARTY"