diff --git a/usr.bin/look/look.1 b/usr.bin/look/look.1
index 8ed43d9ef1de..4c75787d8b52 100644
--- a/usr.bin/look/look.1
+++ b/usr.bin/look/look.1
@@ -109,3 +109,10 @@ utility appeared in
 The
 .Nm
 utility does not recognize multibyte characters.
+.Pp
+Lines are not compared according to the current locale's collating
+order.
+Input files must be sorted with
+.Ev LC_COLLATE
+set to
+.Ql C .