diff --git a/lib/libipsec/ipsec_strerror.3 b/lib/libipsec/ipsec_strerror.3
index 58ac2b6475e0..ba4e6e8e6bf2 100644
--- a/lib/libipsec/ipsec_strerror.3
+++ b/lib/libipsec/ipsec_strerror.3
@@ -37,9 +37,10 @@
 .Nd error code for IPsec policy manipulation library
 .\"
 .Sh SYNOPSIS
+.Fd #include <sys/types.h>
 .Fd #include <netinet6/ipsec.h>
 .Ft "char *"
-.Fn ipsec_strerror
+.Fn ipsec_strerror void
 .\"
 .Sh DESCRIPTION
 .Pa netinet6/ipsec.h