diff --git a/ethchain/asm.go b/ethchain/asm.go
index 277326ff9..09d6af56f 100644
--- a/ethchain/asm.go
+++ b/ethchain/asm.go
@@ -18,7 +18,7 @@ func Disassemble(script []byte) (asm []string) {
 		// Get the opcode (it must be an opcode!)
 		op := OpCode(val)
 
-		asm = append(asm, fmt.Sprintf("%v", op))
+		asm = append(asm, fmt.Sprintf("%04v: %v", pc, op))
 
 		switch op {
 		case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32:
@@ -28,7 +28,7 @@ func Disassemble(script []byte) (asm []string) {
 			if len(data) == 0 {
 				data = []byte{0}
 			}
-			asm = append(asm, fmt.Sprintf("0x%x", data))
+			asm = append(asm, fmt.Sprintf("%04v: 0x%x", pc, data))
 
 			pc.Add(pc, big.NewInt(a-1))
 		}