diff --git a/sys/src/libmach/8db.c b/sys/src/libmach/8db.c
index a2fd4b449..5a2f10a89 100644
--- a/sys/src/libmach/8db.c
+++ b/sys/src/libmach/8db.c
@@ -535,6 +535,7 @@ static Optable optab0F[256]=
 [0x74]	RM,0,		"PCMPEQB %m,%M",
 [0x75]	RM,0,		"PCMPEQW %m,%M",
 [0x76]	RM,0,		"PCMPEQL %m,%M",
+[0x77]	0,0,		"EMMS",
 [0x7E]	RM,0,		"MOV%S %M,%e",
 [0x7F]	RM,0,		"MOVQ %M,%m",
 [0xAE]	RMOP,0,		optab0FAE,