diff --git a/gen/gen_code.cpp b/gen/gen_code.cpp
index 6728a14..8642090 100644
--- a/gen/gen_code.cpp
+++ b/gen/gen_code.cpp
@@ -628,6 +628,7 @@ void put()
 			{ "movsb", 0xA4 },
 			{ "movsw", 0x66, 0xA5 },
 			{ "movsd", 0xA5 },
+			{ "rep", 0xF3 },
 
 			{ "lahf", 0x9F },
 			{ "lock", 0xF0 },
diff --git a/xbyak/xbyak_mnemonic.h b/xbyak/xbyak_mnemonic.h
index 8e97439..2cf91f6 100644
--- a/xbyak/xbyak_mnemonic.h
+++ b/xbyak/xbyak_mnemonic.h
@@ -650,6 +650,7 @@ void rdrand(const Reg& r) { if (r.isBit(8)) throw Error(ERR_BAD_SIZE_OF_REGISTER
 void rdseed(const Reg& r) { if (r.isBit(8)) throw Error(ERR_BAD_SIZE_OF_REGISTER); opModR(Reg(7, Operand::REG, r.getBit()), r, 0x0F, 0xC7); }
 void rdtsc() { db(0x0F); db(0x31); }
 void rdtscp() { db(0x0F); db(0x01); db(0xF9); }
+void rep() { db(0xF3); }
 void ret(int imm = 0) { if (imm) { db(0xC2); dw(imm); } else { db(0xC3); } }
 void rol(const Operand& op, const Reg8& _cl) { opShift(op, _cl, 0); }
 void rol(const Operand& op, int imm) { opShift(op, imm, 0); }