diff --git a/nemu/src/isa/riscv32/inst.c b/nemu/src/isa/riscv32/inst.c
index 99697ed..b51ac55 100644
--- a/nemu/src/isa/riscv32/inst.c
+++ b/nemu/src/isa/riscv32/inst.c
@@ -120,7 +120,7 @@ static int decode_exec(Decode *s) {
   INSTPAT("0000000 00001 00000 000 00000 11100 11", ebreak , N, NEMUTRAP(s->pc, R(10))); // R(10) is $a0
   
   INSTPAT("0000001 ????? ????? 000 ????? 01100 11", mul    , R, R(rd) = (sword_t)src1 * (sword_t)src2);
-  INSTPAT("0000001 ????? ????? 001 ????? 01100 11", mulh   , R, R(rd) = ((int64_t)(sword_t) src1 * (int64_t)(word_t) src2) >> 32);
+  INSTPAT("0000001 ????? ????? 001 ????? 01100 11", mulh   , R, R(rd) = ((int64_t)(sword_t) src1 * (int64_t)(sword_t) src2) >> 32);
   INSTPAT("0000001 ????? ????? 010 ????? 01100 11", mulhsu , R, R(rd) = ((int64_t)(sword_t) src1 * (uint64_t)src2) >> 32); // never used
   INSTPAT("0000001 ????? ????? 011 ????? 01100 11", mulhu  , R, R(rd) = ((uint64_t)src1 * (uint64_t)src2) >> 32); // never used
   INSTPAT("0000001 ????? ????? 100 ????? 01100 11", div    , R, R(rd) = (src1 == INT_MIN && src2 == -1) ? src1 : (src2 ? (sword_t) src1 / (sword_t) src2 : -1));