diff --git a/usr.bin/truss/syscall.h b/usr.bin/truss/syscall.h
index 508e1923d19..574b6a6b5d3 100644
--- a/usr.bin/truss/syscall.h
+++ b/usr.bin/truss/syscall.h
@@ -49,7 +49,7 @@ enum Argtype { None = 1, Hex, Octal, Int, UInt, LongHex, Name, Ptr, Stat, Ioctl,
 	CapFcntlRights, Fadvice, FileFlags, Flockop, Getfsstatmode, Kldsymcmd,
 	Kldunloadflags, Sizet, Madvice, Socklent, Sockprotocol, Sockoptlevel,
 	Sockoptname, Msgflags, CapRights, PUInt, PQuadHex, Acltype,
-	Extattrnamespace, Minherit,
+	Extattrnamespace, Minherit, Mlockall,
 
 	CloudABIAdvice, CloudABIClockID, ClouduABIFDSFlags,
 	CloudABIFDStat, CloudABIFileStat, CloudABIFileType,
diff --git a/usr.bin/truss/syscalls.c b/usr.bin/truss/syscalls.c
index 4e62fa2def5..b68be078b43 100644
--- a/usr.bin/truss/syscalls.c
+++ b/usr.bin/truss/syscalls.c
@@ -313,6 +313,10 @@ static struct syscall decoded_syscalls[] = {
 	  .args = { { Name, 0 }, { Octal, 1 }, { Int, 2 } } },
 	{ .name = "mknodat", .ret_type = 1, .nargs = 4,
 	  .args = { { Atfd, 0 }, { Name, 1 }, { Octal, 2 }, { Int, 3 } } },
+	{ .name = "mlock", .ret_type = 1, .nargs = 2,
+	  .args = { { Ptr, 0 }, { Sizet, 1 } } },
+	{ .name = "mlockall", .ret_type = 1, .nargs = 1,
+	  .args = { { Mlockall, 0 } } },
 	{ .name = "mmap", .ret_type = 1, .nargs = 6,
 	  .args = { { Ptr, 0 }, { Sizet, 1 }, { Mprot, 2 }, { Mmapflags, 3 },
 		    { Int, 4 }, { QuadHex, 5 } } },
@@ -322,6 +326,8 @@ static struct syscall decoded_syscalls[] = {
 	  .args = { { Name, 0 }, { Name, 1 }, { Int, 2 }, { Ptr, 3 } } },
 	{ .name = "mprotect", .ret_type = 1, .nargs = 3,
 	  .args = { { Ptr, 0 }, { Sizet, 1 }, { Mprot, 2 } } },
+	{ .name = "munlock", .ret_type = 1, .nargs = 2,
+	  .args = { { Ptr, 0 }, { Sizet, 1 } } },
 	{ .name = "munmap", .ret_type = 1, .nargs = 2,
 	  .args = { { Ptr, 0 }, { Sizet, 1 } } },
 	{ .name = "nanosleep", .ret_type = 1, .nargs = 1,
@@ -2104,6 +2110,9 @@ print_arg(struct syscall_args *sc, unsigned long *args, long *retval,
 		print_integer_arg(sysdecode_minherit_inherit, fp,
 		    args[sc->offset]);
 		break;
+	case Mlockall:
+		print_mask_arg(sysdecode_mlockall_flags, fp, args[sc->offset]);
+		break;
 
 	case CloudABIAdvice:
 		fputs(xlookup(cloudabi_advice, args[sc->offset]), fp);