diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index c374d27fe4f3..2e133664a05b 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -244,7 +244,7 @@ Arguments:
                 Subcommand::Doc { paths: paths }
             }
             "clean" => {
-                if matches.free.len() > 0 {
+                if paths.len() > 0 {
                     println!("\nclean takes no arguments\n");
                     usage(1, &opts, &subcommand_help, &extra_help);
                 }