diff --git a/lib/libc/sys/swapon.2 b/lib/libc/sys/swapon.2
index 1a64d39f302..c0c12d9dde6 100644
--- a/lib/libc/sys/swapon.2
+++ b/lib/libc/sys/swapon.2
@@ -158,4 +158,4 @@ system call appeared in
 The
 .Fn swapoff
 system call appeared in
-.Fx 5.0 .
+.Fx 5.1 .