diff --git a/usr.bin/truss/syscall.h b/usr.bin/truss/syscall.h
index 14aebd06680..0ed08bde57d 100644
--- a/usr.bin/truss/syscall.h
+++ b/usr.bin/truss/syscall.h
@@ -46,7 +46,7 @@ enum Argtype { None = 1, Hex, Octal, Int, UInt, LongHex, Name, Ptr, Stat, Ioctl,
 	LinuxSockArgs, Umtxop, Atfd, Atflags, Timespec2, Accessmode, Long,
 	Sysarch, ExecArgs, ExecEnv, PipeFds, QuadHex, Utrace, IntArray, Pipe2,
 	CapFcntlRights, Fadvice, FileFlags, Flockop, Getfsstatmode, Kldsymcmd,
-	Kldunloadflags, Sizet,
+	Kldunloadflags, Sizet, Madvice,
 
 	CloudABIAdvice, CloudABIClockID, ClouduABIFDSFlags,
 	CloudABIFDStat, CloudABIFileStat, CloudABIFileType,
diff --git a/usr.bin/truss/syscalls.c b/usr.bin/truss/syscalls.c
index 87be24df220..fce610c7521 100644
--- a/usr.bin/truss/syscalls.c
+++ b/usr.bin/truss/syscalls.c
@@ -218,6 +218,8 @@ static struct syscall decoded_syscalls[] = {
 	  .args = { { Name | IN, 0 }, { Stat | OUT, 1 } } },
 	{ .name = "lutimes", .ret_type = 1, .nargs = 2,
 	  .args = { { Name | IN, 0 }, { Timeval2 | IN, 1 } } },
+	{ .name = "madvise", .ret_type = 1, .nargs = 3,
+	  .args = { { Ptr, 0 }, { Sizet, 1 }, { Madvice, 2 } } },
 	{ .name = "mkdir", .ret_type = 1, .nargs = 2,
 	  .args = { { Name, 0 }, { Octal, 1 } } },
 	{ .name = "mkdirat", .ret_type = 1, .nargs = 3,
@@ -1907,6 +1909,9 @@ print_arg(struct syscall_args *sc, unsigned long *args, long *retval,
 		print_integer_arg(sysdecode_kldunload_flags, fp,
 		    args[sc->offset]);
 		break;
+	case Madvice:
+		print_integer_arg(sysdecode_madvice, fp, args[sc->offset]);
+		break;
 
 	case CloudABIAdvice:
 		fputs(xlookup(cloudabi_advice, args[sc->offset]), fp);