| diff --git a/scapy/contrib/cdp.py b/scapy/contrib/cdp.py | |
| index 9ad15c8a..d9cd08c6 100644 | |
| --- a/scapy/contrib/cdp.py | |
| +++ b/scapy/contrib/cdp.py | |
| @@ -357,7 +357,7 @@ class _CDPChecksum: | |
| This padding is only used for checksum computation. The original | |
| packet should not be altered.""" | |
| if len(pkt) % 2: | |
| - last_chr = pkt[-1] | |
| + last_chr = pkt[len(pkt)-1:] | |
| if last_chr <= b'\x80': | |
| return pkt[:-1] + b'\x00' + last_chr | |
| else: |