diff --git a/src/openai/auth/_workload.py b/src/openai/auth/_workload.py
index 6c142a82ed..c648d457d0 100644
--- a/src/openai/auth/_workload.py
+++ b/src/openai/auth/_workload.py
@@ -54,7 +54,7 @@ def k8s_service_account_token_provider(
 
     def get_token() -> str:
         try:
-            with open(token_file_path, "r") as f:
+            with open(token_file_path, "r", encoding="utf-8") as f:
                 token = f.read().strip()
                 if not token:
                     raise SubjectTokenProviderError(f"The token file at {token_file_path} is empty.")
diff --git a/tests/test_auth.py b/tests/test_auth.py
index 17e9cd814c..3d99afb851 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -154,7 +154,7 @@ def test_workload_identity_exchange_error() -> None:
 
 def test_k8s_service_account_token_provider(tmp_path: Path) -> None:
     token_file = tmp_path / "token"
-    token_file.write_text("my-k8s-token")
+    token_file.write_text("my-k8s-token", encoding="utf-8")
 
     provider = k8s_service_account_token_provider(token_file)