diff --git a/container_option.go b/container_option.go
index 37d2c98..f78b3a0 100644
--- a/container_option.go
+++ b/container_option.go
@@ -83,9 +83,6 @@
 
 // WithDebugOutput sets debug output.
 func WithDebugOutput(w io.Writer) ContainerOption {
-	if w == nil {
-		return nil
-	}
 	return func(s *pState) {
 		s.debugOut = w
 	}