diff --git a/src/openai/_compat.py b/src/openai/_compat.py
index 7c3156a5eb..d7196c9193 100644
--- a/src/openai/_compat.py
+++ b/src/openai/_compat.py
@@ -145,7 +145,8 @@ def model_dump(
             exclude=exclude,
             exclude_unset=exclude_unset,
             exclude_defaults=exclude_defaults,
-            warnings=warnings,
+            # warnings are not supported in Pydantic v1
+            warnings=warnings if PYDANTIC_V2 else True,
         )
     return cast(
         "dict[str, Any]",
diff --git a/tests/test_models.py b/tests/test_models.py
index 84dbce6914..d2884bcbfa 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -561,6 +561,14 @@ class Model(BaseModel):
             m.model_dump(warnings=False)
 
 
+def test_compat_method_no_error_for_warnings() -> None:
+    class Model(BaseModel):
+        foo: Optional[str]
+
+    m = Model(foo="hello")
+    assert isinstance(model_dump(m, warnings=False), dict)
+
+
 def test_to_json() -> None:
     class Model(BaseModel):
         foo: Optional[str] = Field(alias="FOO", default=None)