diff --git a/libs/partners/anthropic/tests/unit_tests/test_chat_models.py b/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
index 0dbdceb483e..9d9518f0ba1 100644
--- a/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
+++ b/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
@@ -42,19 +42,22 @@ MODEL_NAME = "claude-sonnet-4-5-20250929"
 
 def test_initialization() -> None:
     """Test chat model initialization."""
-    for model in [
-        ChatAnthropic(model_name=MODEL_NAME, api_key="xyz", timeout=2),  # type: ignore[arg-type, call-arg]
-        ChatAnthropic(  # type: ignore[call-arg, call-arg, call-arg]
-            model=MODEL_NAME,
-            anthropic_api_key="xyz",
-            default_request_timeout=2,
-            base_url="https://api.anthropic.com",
-        ),
-    ]:
-        assert model.model == MODEL_NAME
-        assert cast("SecretStr", model.anthropic_api_key).get_secret_value() == "xyz"
-        assert model.default_request_timeout == 2.0
-        assert model.anthropic_api_url == "https://api.anthropic.com"
+    with patch.dict(os.environ, {"ANTHROPIC_API_URL": "https://api.anthropic.com"}):
+        for model in [
+            ChatAnthropic(model_name=MODEL_NAME, api_key="xyz", timeout=2),  # type: ignore[arg-type, call-arg]
+            ChatAnthropic(  # type: ignore[call-arg, call-arg, call-arg]
+                model=MODEL_NAME,
+                anthropic_api_key="xyz",
+                default_request_timeout=2,
+                base_url="https://api.anthropic.com",
+            ),
+        ]:
+            assert model.model == MODEL_NAME
+            assert (
+                cast("SecretStr", model.anthropic_api_key).get_secret_value() == "xyz"
+            )
+            assert model.default_request_timeout == 2.0
+            assert model.anthropic_api_url == "https://api.anthropic.com"
 
 
 def test_user_agent_header_in_client_params() -> None:
diff --git a/libs/partners/anthropic/tests/unit_tests/test_standard.py b/libs/partners/anthropic/tests/unit_tests/test_standard.py
index 75b393dfbdd..77bc50e76c8 100644
--- a/libs/partners/anthropic/tests/unit_tests/test_standard.py
+++ b/libs/partners/anthropic/tests/unit_tests/test_standard.py
@@ -19,12 +19,15 @@ class TestAnthropicStandard(ChatModelUnitTests):
 
     @property
     def chat_model_params(self) -> dict:
-        return {"model": _MODEL}
+        return {"model": _MODEL, "base_url": "https://api.anthropic.com"}
 
     @property
     def init_from_env_params(self) -> tuple[dict, dict, dict]:
         return (
-            {"ANTHROPIC_API_KEY": "test"},
+            {
+                "ANTHROPIC_API_KEY": "test",
+                "ANTHROPIC_API_URL": "https://api.anthropic.com",
+            },
             {"model": _MODEL},
             {"anthropic_api_key": "test"},
         )