diff --git a/nemu/src/isa/riscv32/inst.c b/nemu/src/isa/riscv32/inst.c
index 1dd92ab..b79bb00 100644
--- a/nemu/src/isa/riscv32/inst.c
+++ b/nemu/src/isa/riscv32/inst.c
@@ -33,7 +33,7 @@ enum {
 #define immI() do { *imm = SEXT(BITS(i, 31, 20), 12); } while(0)
 #define immU() do { *imm = SEXT(BITS(i, 31, 12), 20) << 12; } while(0)
 #define immS() do { *imm = (SEXT(BITS(i, 31, 25), 7) << 5) | BITS(i, 11, 7); } while(0)
-#define immB() do { *imm = (SEXT(BITS(i, 31, 31), 1) << 12 | BITS(i, 30, 25) << 5 | BITS(i, 11, 8) << 1 | BITS(i, 8, 8) << 11; } while(0)
+#define immB() do { *imm = (SEXT(BITS(i, 31, 31), 1) << 12 | BITS(i, 30, 25) << 5 | BITS(i, 11, 8) << 1 | BITS(i, 8, 8) << 11); } while(0)
 #define immJ() do { *imm = (SEXT(BITS(i, 31, 31), 1) << 20) | BITS(i, 30, 21) << 1 | BITS(i, 20, 20) << 11 | BITS(i, 19, 12) << 12; } while(0)
 
 static void decode_operand(Decode *s, int *rd, word_t *src1, word_t *src2, word_t *imm, int type) {
@@ -47,6 +47,7 @@ static void decode_operand(Decode *s, int *rd, word_t *src1, word_t *src2, word_
     case TYPE_U:                   immU(); break;
     case TYPE_J:                   immJ(); break;
     case TYPE_S: src1R(); src2R(); immS(); break;
+    case TYPE_B: src1R(); src2R(); immB(); break;
   }
 }