diff --git a/onnxscript/converter.py b/onnxscript/converter.py
index f155f87a10..2d10a73764 100644
--- a/onnxscript/converter.py
+++ b/onnxscript/converter.py
@@ -942,7 +942,6 @@ def _translate_callee_expr(self, node: ast.AST) -> values.Op:  # pylint: disable
             opname = node.attr
             if opname in module:
                 return values.Op(module, node.attr)
-            warn(f"'{opname}' is not a known op in '{module}'")
             return values.Op(module, node.attr)
         if isinstance(node, ast.Name):
             function_name = node.id
diff --git a/onnxscript/values.py b/onnxscript/values.py
index 89fe1e478c..9907b16ee4 100644
--- a/onnxscript/values.py
+++ b/onnxscript/values.py
@@ -109,8 +109,6 @@ def __getattr__(self, attr: str):
             raise AttributeError(f"Attribute {attr} not found.") from exc
 
     def add_function_def(self, fun):
-        if fun.name in self.function_defs:
-            logger.warning("%s: Already defined.", fun.name)
         self.function_defs[fun.name] = fun
 
     def _prepare_inputs(self, _: onnx.defs.OpSchema, *inputs):