diff --git a/lib/libc/aarch64/sys/Makefile.inc b/lib/libc/aarch64/sys/Makefile.inc
--- a/lib/libc/aarch64/sys/Makefile.inc
+++ b/lib/libc/aarch64/sys/Makefile.inc
@@ -8,5 +8,4 @@
 	vfork.S
 
 # Don't generate default code for these syscalls:
-NOASM+=	sbrk.o \
-	vfork.o
+NOASM+=	vfork.o
diff --git a/lib/libc/amd64/sys/Makefile.inc b/lib/libc/amd64/sys/Makefile.inc
--- a/lib/libc/amd64/sys/Makefile.inc
+++ b/lib/libc/amd64/sys/Makefile.inc
@@ -7,4 +7,4 @@
 MDASM=	vfork.S cerror.S getcontext.S
 
 # Don't generate default code for these syscalls:
-NOASM+=	sbrk.o vfork.o
+NOASM+=	vfork.o
diff --git a/lib/libc/arm/sys/Makefile.inc b/lib/libc/arm/sys/Makefile.inc
--- a/lib/libc/arm/sys/Makefile.inc
+++ b/lib/libc/arm/sys/Makefile.inc
@@ -4,4 +4,4 @@
 MDASM= Ovfork.S cerror.S syscall.S
 
 # Don't generate default code for these syscalls:
-NOASM+=	sbrk.o vfork.o
+NOASM+=	vfork.o
diff --git a/lib/libc/i386/sys/Makefile.inc b/lib/libc/i386/sys/Makefile.inc
--- a/lib/libc/i386/sys/Makefile.inc
+++ b/lib/libc/i386/sys/Makefile.inc
@@ -4,7 +4,7 @@
 
 MDASM=	Ovfork.S cerror.S getcontext.S syscall.S
 
-NOASM+=	sbrk.o vfork.o
+NOASM+=	vfork.o
 
 MAN+=	i386_get_ioperm.2 i386_get_ldt.2 i386_vm86.2
 MAN+=	i386_set_watch.3
diff --git a/lib/libc/riscv/sys/Makefile.inc b/lib/libc/riscv/sys/Makefile.inc
--- a/lib/libc/riscv/sys/Makefile.inc
+++ b/lib/libc/riscv/sys/Makefile.inc
@@ -6,4 +6,4 @@
 	vfork.S
 
 # Don't generate default code for these syscalls:
-NOASM+=	sbrk.o vfork.o
+NOASM+=	vfork.o
diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc
--- a/lib/libc/sys/Makefile.inc
+++ b/lib/libc/sys/Makefile.inc
@@ -17,7 +17,6 @@
 #
 NOASM=	exit.o \
 	getlogin.o \
-	sstk.o \
 	yield.o
 PSEUDO=	_exit.o \
 	_getlogin.o
diff --git a/sys/compat/freebsd32/freebsd32_syscall.h b/sys/compat/freebsd32/freebsd32_syscall.h
--- a/sys/compat/freebsd32/freebsd32_syscall.h
+++ b/sys/compat/freebsd32/freebsd32_syscall.h
@@ -73,8 +73,8 @@
 #define	FREEBSD32_SYS_vfork	66
 				/* 67 is obsolete vread */
 				/* 68 is obsolete vwrite */
-#define	FREEBSD32_SYS_sbrk	69
-#define	FREEBSD32_SYS_sstk	70
+				/* 69 is obsolete sbrk */
+				/* 70 is obsolete sstk */
 				/* 71 is old freebsd32_mmap */
 #define	FREEBSD32_SYS_freebsd11_vadvise	72
 #define	FREEBSD32_SYS_munmap	73
diff --git a/sys/compat/freebsd32/freebsd32_syscalls.c b/sys/compat/freebsd32/freebsd32_syscalls.c
--- a/sys/compat/freebsd32/freebsd32_syscalls.c
+++ b/sys/compat/freebsd32/freebsd32_syscalls.c
@@ -74,8 +74,8 @@
 	"vfork",			/* 66 = vfork */
 	"obs_vread",			/* 67 = obsolete vread */
 	"obs_vwrite",			/* 68 = obsolete vwrite */
-	"sbrk",			/* 69 = sbrk */
-	"sstk",			/* 70 = sstk */
+	"obs_sbrk",			/* 69 = obsolete sbrk */
+	"obs_sstk",			/* 70 = obsolete sstk */
 	"compat.freebsd32_mmap",		/* 71 = old freebsd32_mmap */
 	"compat11.vadvise",		/* 72 = freebsd11 vadvise */
 	"munmap",			/* 73 = munmap */
diff --git a/sys/compat/freebsd32/freebsd32_sysent.c b/sys/compat/freebsd32/freebsd32_sysent.c
--- a/sys/compat/freebsd32/freebsd32_sysent.c
+++ b/sys/compat/freebsd32/freebsd32_sysent.c
@@ -130,8 +130,8 @@
 	{ .sy_narg = 0, .sy_call = (sy_call_t *)sys_vfork, .sy_auevent = AUE_VFORK, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 66 = vfork */
 	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 67 = obsolete vread */
 	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 68 = obsolete vwrite */
-	{ .sy_narg = AS(sbrk_args), .sy_call = (sy_call_t *)sys_sbrk, .sy_auevent = AUE_SBRK, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 69 = sbrk */
-	{ .sy_narg = AS(sstk_args), .sy_call = (sy_call_t *)sys_sstk, .sy_auevent = AUE_SSTK, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 70 = sstk */
+	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 69 = obsolete sbrk */
+	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 70 = obsolete sstk */
 	{ compat(AS(ofreebsd32_mmap_args),freebsd32_mmap), .sy_auevent = AUE_MMAP, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 71 = old freebsd32_mmap */
 	{ compat11(AS(freebsd11_vadvise_args),vadvise), .sy_auevent = AUE_O_VADVISE, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 72 = freebsd11 vadvise */
 	{ .sy_narg = AS(munmap_args), .sy_call = (sy_call_t *)sys_munmap, .sy_auevent = AUE_MUNMAP, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 73 = munmap */
diff --git a/sys/compat/freebsd32/freebsd32_systrace_args.c b/sys/compat/freebsd32/freebsd32_systrace_args.c
--- a/sys/compat/freebsd32/freebsd32_systrace_args.c
+++ b/sys/compat/freebsd32/freebsd32_systrace_args.c
@@ -421,20 +421,6 @@
 		*n_args = 0;
 		break;
 	}
-	/* sbrk */
-	case 69: {
-		struct sbrk_args *p = params;
-		iarg[a++] = p->incr; /* int */
-		*n_args = 1;
-		break;
-	}
-	/* sstk */
-	case 70: {
-		struct sstk_args *p = params;
-		iarg[a++] = p->incr; /* int */
-		*n_args = 1;
-		break;
-	}
 	/* munmap */
 	case 73: {
 		struct munmap_args *p = params;
@@ -4009,26 +3995,6 @@
 	/* vfork */
 	case 66:
 		break;
-	/* sbrk */
-	case 69:
-		switch (ndx) {
-		case 0:
-			p = "int";
-			break;
-		default:
-			break;
-		};
-		break;
-	/* sstk */
-	case 70:
-		switch (ndx) {
-		case 0:
-			p = "int";
-			break;
-		default:
-			break;
-		};
-		break;
 	/* munmap */
 	case 73:
 		switch (ndx) {
@@ -9347,16 +9313,6 @@
 		break;
 	/* vfork */
 	case 66:
-	/* sbrk */
-	case 69:
-		if (ndx == 0 || ndx == 1)
-			p = "int";
-		break;
-	/* sstk */
-	case 70:
-		if (ndx == 0 || ndx == 1)
-			p = "int";
-		break;
 	/* munmap */
 	case 73:
 		if (ndx == 0 || ndx == 1)
diff --git a/sys/kern/init_sysent.c b/sys/kern/init_sysent.c
--- a/sys/kern/init_sysent.c
+++ b/sys/kern/init_sysent.c
@@ -129,8 +129,8 @@
 	{ .sy_narg = 0, .sy_call = (sy_call_t *)sys_vfork, .sy_auevent = AUE_VFORK, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 66 = vfork */
 	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 67 = obsolete vread */
 	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 68 = obsolete vwrite */
-	{ .sy_narg = AS(sbrk_args), .sy_call = (sy_call_t *)sys_sbrk, .sy_auevent = AUE_SBRK, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 69 = sbrk */
-	{ .sy_narg = AS(sstk_args), .sy_call = (sy_call_t *)sys_sstk, .sy_auevent = AUE_SSTK, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 70 = sstk */
+	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 69 = obsolete sbrk */
+	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 70 = obsolete sstk */
 	{ compat(AS(ommap_args),mmap), .sy_auevent = AUE_MMAP, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 71 = old mmap */
 	{ compat11(AS(freebsd11_vadvise_args),vadvise), .sy_auevent = AUE_O_VADVISE, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 72 = freebsd11 vadvise */
 	{ .sy_narg = AS(munmap_args), .sy_call = (sy_call_t *)sys_munmap, .sy_auevent = AUE_MUNMAP, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 73 = munmap */
diff --git a/sys/kern/syscalls.c b/sys/kern/syscalls.c
--- a/sys/kern/syscalls.c
+++ b/sys/kern/syscalls.c
@@ -74,8 +74,8 @@
 	"vfork",			/* 66 = vfork */
 	"obs_vread",			/* 67 = obsolete vread */
 	"obs_vwrite",			/* 68 = obsolete vwrite */
-	"sbrk",			/* 69 = sbrk */
-	"sstk",			/* 70 = sstk */
+	"obs_sbrk",			/* 69 = obsolete sbrk */
+	"obs_sstk",			/* 70 = obsolete sstk */
 	"compat.mmap",		/* 71 = old mmap */
 	"compat11.vadvise",		/* 72 = freebsd11 vadvise */
 	"munmap",			/* 73 = munmap */
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -502,16 +502,8 @@
 	}
 67	AUE_NULL	OBSOL	vread
 68	AUE_NULL	OBSOL	vwrite
-69	AUE_SBRK	STD|CAPENABLED {
-		int sbrk(
-		    int incr
-		);
-	}
-70	AUE_SSTK	STD|CAPENABLED {
-		int sstk(
-		    int incr
-		);
-	}
+69	AUE_NULL	OBSOL	sbrk
+70	AUE_NULL	OBSOL	sstk
 71	AUE_MMAP	COMPAT|CAPENABLED {
 		void *mmap(
 		    _In_ void *addr,
diff --git a/sys/kern/systrace_args.c b/sys/kern/systrace_args.c
--- a/sys/kern/systrace_args.c
+++ b/sys/kern/systrace_args.c
@@ -418,20 +418,6 @@
 		*n_args = 0;
 		break;
 	}
-	/* sbrk */
-	case 69: {
-		struct sbrk_args *p = params;
-		iarg[a++] = p->incr; /* int */
-		*n_args = 1;
-		break;
-	}
-	/* sstk */
-	case 70: {
-		struct sstk_args *p = params;
-		iarg[a++] = p->incr; /* int */
-		*n_args = 1;
-		break;
-	}
 	/* munmap */
 	case 73: {
 		struct munmap_args *p = params;
@@ -4096,26 +4082,6 @@
 	/* vfork */
 	case 66:
 		break;
-	/* sbrk */
-	case 69:
-		switch (ndx) {
-		case 0:
-			p = "int";
-			break;
-		default:
-			break;
-		};
-		break;
-	/* sstk */
-	case 70:
-		switch (ndx) {
-		case 0:
-			p = "int";
-			break;
-		default:
-			break;
-		};
-		break;
 	/* munmap */
 	case 73:
 		switch (ndx) {
@@ -9492,16 +9458,6 @@
 		break;
 	/* vfork */
 	case 66:
-	/* sbrk */
-	case 69:
-		if (ndx == 0 || ndx == 1)
-			p = "int";
-		break;
-	/* sstk */
-	case 70:
-		if (ndx == 0 || ndx == 1)
-			p = "int";
-		break;
 	/* munmap */
 	case 73:
 		if (ndx == 0 || ndx == 1)
diff --git a/sys/sys/syscall.h b/sys/sys/syscall.h
--- a/sys/sys/syscall.h
+++ b/sys/sys/syscall.h
@@ -73,8 +73,8 @@
 #define	SYS_vfork	66
 				/* 67 is obsolete vread */
 				/* 68 is obsolete vwrite */
-#define	SYS_sbrk	69
-#define	SYS_sstk	70
+				/* 69 is obsolete sbrk */
+				/* 70 is obsolete sstk */
 				/* 71 is old mmap */
 #define	SYS_freebsd11_vadvise	72
 #define	SYS_munmap	73
diff --git a/sys/sys/syscall.mk b/sys/sys/syscall.mk
--- a/sys/sys/syscall.mk
+++ b/sys/sys/syscall.mk
@@ -56,8 +56,6 @@
 	chroot.o \
 	msync.o \
 	vfork.o \
-	sbrk.o \
-	sstk.o \
 	freebsd11_vadvise.o \
 	munmap.o \
 	mprotect.o \
diff --git a/sys/sys/sysproto.h b/sys/sys/sysproto.h
--- a/sys/sys/sysproto.h
+++ b/sys/sys/sysproto.h
@@ -254,12 +254,6 @@
 struct vfork_args {
 	syscallarg_t dummy;
 };
-struct sbrk_args {
-	char incr_l_[PADL_(int)]; int incr; char incr_r_[PADR_(int)];
-};
-struct sstk_args {
-	char incr_l_[PADL_(int)]; int incr; char incr_r_[PADR_(int)];
-};
 struct munmap_args {
 	char addr_l_[PADL_(void *)]; void * addr; char addr_r_[PADR_(void *)];
 	char len_l_[PADL_(size_t)]; size_t len; char len_r_[PADR_(size_t)];
@@ -1928,8 +1922,6 @@
 int	sys_chroot(struct thread *, struct chroot_args *);
 int	sys_msync(struct thread *, struct msync_args *);
 int	sys_vfork(struct thread *, struct vfork_args *);
-int	sys_sbrk(struct thread *, struct sbrk_args *);
-int	sys_sstk(struct thread *, struct sstk_args *);
 int	sys_munmap(struct thread *, struct munmap_args *);
 int	sys_mprotect(struct thread *, struct mprotect_args *);
 int	sys_madvise(struct thread *, struct madvise_args *);
@@ -2838,8 +2830,6 @@
 #define	SYS_AUE_ogetpagesize	AUE_NULL
 #define	SYS_AUE_msync	AUE_MSYNC
 #define	SYS_AUE_vfork	AUE_VFORK
-#define	SYS_AUE_sbrk	AUE_SBRK
-#define	SYS_AUE_sstk	AUE_SSTK
 #define	SYS_AUE_ommap	AUE_MMAP
 #define	SYS_AUE_freebsd11_vadvise	AUE_O_VADVISE
 #define	SYS_AUE_munmap	AUE_MUNMAP
diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -106,32 +106,6 @@
 
 _Static_assert(MAXPAGESIZES <= 4, "MINCORE_SUPER too narrow");
 
-#ifndef _SYS_SYSPROTO_H_
-struct sbrk_args {
-	int incr;
-};
-#endif
-
-int
-sys_sbrk(struct thread *td, struct sbrk_args *uap)
-{
-	/* Not yet implemented */
-	return (EOPNOTSUPP);
-}
-
-#ifndef _SYS_SYSPROTO_H_
-struct sstk_args {
-	int incr;
-};
-#endif
-
-int
-sys_sstk(struct thread *td, struct sstk_args *uap)
-{
-	/* Not yet implemented */
-	return (EOPNOTSUPP);
-}
-
 #if defined(COMPAT_43)
 int
 ogetpagesize(struct thread *td, struct ogetpagesize_args *uap)