diff --git a/ethchain/asm.go b/ethchain/asm.go
index 277326ff93..09d6af56fc 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))
 		}