diff --git a/share/man/man9/vm_map_protect.9 b/share/man/man9/vm_map_protect.9
index c4b5a738abe7..2c8b52f7e420 100644
--- a/share/man/man9/vm_map_protect.9
+++ b/share/man/man9/vm_map_protect.9
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 19, 2003
+.Dd June 20, 2019
 .Dt VM_MAP_PROTECT 9
 .Os
 .Sh NAME
@@ -51,6 +51,11 @@ within the map
 .Fa map
 to
 .Fa new_prot .
+The value specified by
+.Fa new_prot
+may not include any protection bits that are not set in
+.Va max_protection
+on every entry within the range.
 .Pp
 If
 .Fa set_max