diff --git a/src/spdl/dataloader/_builder.py b/src/spdl/dataloader/_builder.py
index 40d4a434..d3e81fcf 100644
--- a/src/spdl/dataloader/_builder.py
+++ b/src/spdl/dataloader/_builder.py
@@ -264,6 +264,9 @@ def _ordered_pipe(
         else hooks
     )
 
+    # This has been checked in `PipelineBuilder.pipe()`
+    assert not inspect.isasyncgenfunction(op)
+
     afunc = _convert.convert_to_async(op, executor)
 
     async def _wrap(item: T) -> asyncio.Task[U]:
@@ -634,13 +637,15 @@ def pipe(
                 f"Found: {output_order}"
             )
 
-        if name is None:
-            if hasattr(op, "__name__"):
-                name = op.__name__  # type: ignore[attr-defined]
-            else:
-                name = op.__class__.__name__
-
-        _convert.validate_op(op, executor, output_order)
+        if inspect.iscoroutinefunction(op) or inspect.isasyncgenfunction(op):
+            if executor is not None:
+                raise ValueError("`executor` cannot be specified when op is async.")
+        if inspect.isasyncgenfunction(op):
+            if output_order == "input":
+                raise ValueError(
+                    "pipe does not support async generator function "
+                    "when `output_order` is 'input'."
+                )
 
         self._process_args.append(
             (
@@ -649,7 +654,7 @@ def pipe(
                     "op": op,
                     "executor": executor,
                     "concurrency": concurrency,
-                    "name": name,
+                    "name": name or getattr(op, "__name__", op.__class__.__name__),
                     "hooks": hooks,
                     "report_stats_interval": report_stats_interval,
                 },
diff --git a/src/spdl/dataloader/_convert.py b/src/spdl/dataloader/_convert.py
index 5b844176..9729dfbc 100644
--- a/src/spdl/dataloader/_convert.py
+++ b/src/spdl/dataloader/_convert.py
@@ -93,28 +93,13 @@ def _next() -> U:
     return afunc
 
 
-def validate_op(
-    op: Callables[T, U],
-    executor: type[Executor] | None,
-    output_order: str,
-) -> None:
-    if inspect.iscoroutinefunction(op) or inspect.isasyncgenfunction(op):
-        if executor is not None:
-            raise ValueError("`executor` cannot be specified when op is async.")
-    if inspect.isasyncgenfunction(op):
-        if output_order == "input":
-            raise ValueError(
-                "pipe does not support async generator function "
-                "when output_order is 'input'."
-            )
-
-
 def convert_to_async(
     op: Callables[T, U],
     executor: type[Executor] | None,
 ) -> AsyncCallables[T, U]:
     if inspect.iscoroutinefunction(op) or inspect.isasyncgenfunction(op):
         # op is async function. No need to convert.
+        assert executor is None  # This has been checked in `PipelineBuilder.pipe()`
         return op  # pyre-ignore: [7]
 
     if inspect.isgeneratorfunction(op):