diff --git a/flake.nix b/flake.nix
index 69b4884..990d66d 100644
--- a/flake.nix
+++ b/flake.nix
@@ -61,6 +61,15 @@
             gdb
           ] ++ builtins.attrValues self.packages.${system};
         };
+        
+        devShells.nemu = pkgs.mkShell {
+          packages = with pkgs; [
+            clang-tools
+          ];
+          inputsFrom = [
+            self.packages.${system}.nemu
+          ];
+        };
       }
     );
 }
diff --git a/nemu/src/isa/riscv32/inst.c b/nemu/src/isa/riscv32/inst.c
index 39e0e08..7d7d8e7 100644
--- a/nemu/src/isa/riscv32/inst.c
+++ b/nemu/src/isa/riscv32/inst.c
@@ -48,6 +48,11 @@ static void decode_operand(Decode *s, int *rd, word_t *src1, word_t *src2, word_
   }
 }
 
+static void do_jump(Decode *s, int rd, int relative_address) {
+  R(rd) = s->pc + 4;
+  s->dnpc = s->pc + relative_address;
+}
+
 static int decode_exec(Decode *s) {
   int rd = 0;
   word_t src1 = 0, src2 = 0, imm = 0;
@@ -62,8 +67,8 @@ static int decode_exec(Decode *s) {
   INSTPAT_START();
   INSTPAT("??????? ????? ????? ??? ????? 01101 11", lui    , U, R(rd) = imm);
   INSTPAT("??????? ????? ????? ??? ????? 00101 11", auipc  , U, R(rd) = s->pc + imm);
-  // INSTPAT("??????? ????? ????? ??? ????? 11011 11", jal,   , J, do {s->dnpc = s->pc + imm; R(rd) = s->pc + 4; } while(0));
-  // INSTPAT("??????? ????? ????? ??? ????? 11001 11", jalr   , I, do {s->dnpc = s->pc + src1; R(rd) = s->pc + 4); } while(0);
+  // INSTPAT("??????? ????? ????? ??? ????? 11011 11", jal,   , J, do_jump(s, rd, imm) );
+  INSTPAT("??????? ????? ????? ??? ????? 11001 11", jalr   , I, do_jump(s, rd, imm) );
   INSTPAT("??????? ????? ????? 100 ????? 00000 11", lbu    , I, R(rd) = Mr(src1 + imm, 1));
   INSTPAT("??????? ????? ????? 000 ????? 01000 11", sb     , S, Mw(src1 + imm, 1, src2));
   INSTPAT("??????? ????? ????? 000 ????? 00100 11", addi   , I, R(rd) = src1 + (sword_t)imm);