Index: bin/sh/jobs.c
===================================================================
--- bin/sh/jobs.c
+++ bin/sh/jobs.c
@@ -911,6 +911,9 @@
 		int wasroot;
 		int i;
 
+		if (Sflag)
+			(void)setsid();
+
 		TRACE(("Child shell %d\n", (int)getpid()));
 		wasroot = rootshell;
 		rootshell = 0;
Index: bin/sh/options.h
===================================================================
--- bin/sh/options.h
+++ bin/sh/options.h
@@ -68,15 +68,16 @@
 #define	hflag optval[18]
 #define	nologflag optval[19]
 #define	pipefailflag optval[20]
+#define	Sflag optval[21]
 
-#define NSHORTOPTS	19
-#define NOPTS		21
+#define NSHORTOPTS	20
+#define NOPTS		22
 
 extern char optval[NOPTS];
 extern const char optletter[NSHORTOPTS];
 #ifdef DEFINE_OPTIONS
 char optval[NOPTS];
-const char optletter[NSHORTOPTS] = "efIimnsxvVECabupTPh";
+const char optletter[NSHORTOPTS] = "efIimnsxvVECabupTPhS";
 static const unsigned char optname[] =
 	"\007errexit"
 	"\006noglob"
@@ -97,6 +98,7 @@
 	"\012trapsasync"
 	"\010physical"
 	"\010trackall"
+	"\006setsid"
 	"\005nolog"
 	"\010pipefail"
 ;
Index: bin/sh/options.c
===================================================================
--- bin/sh/options.c
+++ bin/sh/options.c
@@ -297,6 +297,8 @@
 			Eflag = 0;
 		else if (&optval[idx] == &Eflag)
 			Vflag = 0;
+		else if (&optval[idx] == &Sflag)
+			Sflag = 1;
 	}
 }
 
Index: bin/sh/sh.1
===================================================================
--- bin/sh/sh.1
+++ bin/sh/sh.1
@@ -32,7 +32,7 @@
 .\"	from: @(#)sh.1	8.6 (Berkeley) 5/4/95
 .\" $FreeBSD$
 .\"
-.Dd July 6, 2020
+.Dd March 10, 2021
 .Dt SH 1
 .Os
 .Sh NAME
@@ -40,14 +40,14 @@
 .Nd command interpreter (shell)
 .Sh SYNOPSIS
 .Nm
-.Op Fl /+abCEefhIimnPpTuVvx
+.Op Fl /+abCEefhIimnPpSTuVvx
 .Op Fl /+o Ar longname
 .Oo
 .Ar script
 .Op Ar arg ...
 .Oc
 .Nm
-.Op Fl /+abCEefhIimnPpTuVvx
+.Op Fl /+abCEefhIimnPpSTuVvx
 .Op Fl /+o Ar longname
 .Fl c Ar string
 .Oo
@@ -55,7 +55,7 @@
 .Op Ar arg ...
 .Oc
 .Nm
-.Op Fl /+abCEefhIimnPpTuVvx
+.Op Fl /+abCEefhIimnPpSTuVvx
 .Op Fl /+o Ar longname
 .Fl s
 .Op Ar arg ...
@@ -302,6 +302,10 @@
 running (i.e., when set with the
 .Ic set
 command).
+.It Fl S
+When doing job control, call
+.Xr setsid 2
+to create a new session.
 .It Fl T Li trapsasync
 When waiting for a child, execute traps immediately.
 If this option is not set,