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
@@ -326,6 +326,7 @@
 #define	FREEBSD32_SYS_lchflags	391
 #define	FREEBSD32_SYS_uuidgen	392
 #define	FREEBSD32_SYS_freebsd32_sendfile	393
+#define	FREEBSD32_SYS_mac_syscall	394
 #define	FREEBSD32_SYS_freebsd11_freebsd32_getfsstat	395
 #define	FREEBSD32_SYS_freebsd11_statfs	396
 #define	FREEBSD32_SYS_freebsd11_fstatfs	397
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
@@ -399,7 +399,7 @@
 	"lchflags",			/* 391 = lchflags */
 	"uuidgen",			/* 392 = uuidgen */
 	"freebsd32_sendfile",			/* 393 = freebsd32_sendfile */
-	"#394",			/* 394 = mac_syscall */
+	"mac_syscall",			/* 394 = mac_syscall */
 	"compat11.freebsd32_getfsstat",		/* 395 = freebsd11 freebsd32_getfsstat */
 	"compat11.statfs",		/* 396 = freebsd11 statfs */
 	"compat11.fstatfs",		/* 397 = freebsd11 fstatfs */
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
@@ -455,7 +455,7 @@
 	{ .sy_narg = AS(lchflags_args), .sy_call = (sy_call_t *)sys_lchflags, .sy_auevent = AUE_LCHFLAGS, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 391 = lchflags */
 	{ .sy_narg = AS(uuidgen_args), .sy_call = (sy_call_t *)sys_uuidgen, .sy_auevent = AUE_NULL, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 392 = uuidgen */
 	{ .sy_narg = AS(freebsd32_sendfile_args), .sy_call = (sy_call_t *)freebsd32_sendfile, .sy_auevent = AUE_SENDFILE, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 393 = freebsd32_sendfile */
-	{ .sy_narg = 0, .sy_call = (sy_call_t *)nosys, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_ABSENT },			/* 394 = mac_syscall */
+	{ .sy_narg = AS(mac_syscall_args), .sy_call = (sy_call_t *)sys_mac_syscall, .sy_auevent = AUE_NULL, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 394 = mac_syscall */
 	{ compat11(AS(freebsd11_freebsd32_getfsstat_args),freebsd32_getfsstat), .sy_auevent = AUE_GETFSSTAT, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 395 = freebsd11 freebsd32_getfsstat */
 	{ compat11(AS(freebsd11_statfs_args),statfs), .sy_auevent = AUE_STATFS, .sy_flags = 0, .sy_thrcnt = SY_THR_STATIC },	/* 396 = freebsd11 statfs */
 	{ compat11(AS(freebsd11_fstatfs_args),fstatfs), .sy_auevent = AUE_FSTATFS, .sy_flags = SYF_CAPENABLED, .sy_thrcnt = SY_THR_STATIC },	/* 397 = freebsd11 fstatfs */
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
@@ -1848,6 +1848,15 @@
 		*n_args = 8;
 		break;
 	}
+	/* mac_syscall */
+	case 394: {
+		struct mac_syscall_args *p = params;
+		uarg[a++] = (intptr_t)p->policy; /* const char * */
+		iarg[a++] = p->call; /* int */
+		uarg[a++] = (intptr_t)p->arg; /* void * */
+		*n_args = 3;
+		break;
+	}
 	/* ksem_close */
 	case 400: {
 		struct ksem_close_args *p = params;
@@ -6293,6 +6302,22 @@
 			break;
 		};
 		break;
+	/* mac_syscall */
+	case 394:
+		switch (ndx) {
+		case 0:
+			p = "userland const char *";
+			break;
+		case 1:
+			p = "int";
+			break;
+		case 2:
+			p = "userland void *";
+			break;
+		default:
+			break;
+		};
+		break;
 	/* ksem_close */
 	case 400:
 		switch (ndx) {
@@ -10049,6 +10074,11 @@
 		if (ndx == 0 || ndx == 1)
 			p = "int";
 		break;
+	/* mac_syscall */
+	case 394:
+		if (ndx == 0 || ndx == 1)
+			p = "int";
+		break;
 	/* ksem_close */
 	case 400:
 		if (ndx == 0 || ndx == 1)
diff --git a/sys/compat/freebsd32/syscalls.conf b/sys/compat/freebsd32/syscalls.conf
--- a/sys/compat/freebsd32/syscalls.conf
+++ b/sys/compat/freebsd32/syscalls.conf
@@ -47,7 +47,7 @@
 obsol="getkerninfo"
 
 # Syscalls without implementations:
-# *mac_* - should be implemented
+# __mac_* - should be implemented
 # afs3_syscall - requires significant porting, probably doesn't make sense
 # kldsym - can't be implemented (kernel virtual addresses can't fit in 32-bits)
 # lgetfh - should be implemented
@@ -55,4 +55,4 @@
 # nnpfs_syscall - requires significant porting, probably doesn't make sense
 # ntp_gettime - should be implemented
 # thr_create - was unimplemented and appears to be unnecessicary
-unimpl="afs3_syscall kldsym __mac_get_proc __mac_set_proc __mac_get_fd __mac_get_file __mac_set_fd __mac_set_file __mac_get_pid __mac_get_link __mac_set_link __mac_execve mac_syscall nfssvc nlm_syscall ntp_gettime lgetfh nnpfs_syscall thr_create"
+unimpl="afs3_syscall kldsym __mac_get_proc __mac_set_proc __mac_get_fd __mac_get_file __mac_set_fd __mac_set_file __mac_get_pid __mac_get_link __mac_set_link __mac_execve nfssvc nlm_syscall ntp_gettime lgetfh nnpfs_syscall thr_create"