diff --git a/README b/README
index a954bb3..ce00b50 100644
--- a/README
+++ b/README
@@ -18,6 +18,9 @@ It requires the following utilities:
   mv
   sed
 
+This requires a recent version of mv that supports the -n
+(--no-clobber) option.
+
 Usage: trash [OPTION]... FILE...
 
 Move files into the trash.