nmap dhcp-discover script broken

Step to reproduce:

Log in as root.

# nmap -sU -p 67 -v -d -PN --script=dhcp-discover <a dhcp server>

Starting Nmap 6.40 ( http://nmap.org ) at 2015-07-01 07:21 CEST
--------------- Timing report ---------------
  hostgroups: min 1, max 100000
  rtt-timeouts: init 1000, min 100, max 10000
  max-scan-delay: TCP 1000, UDP 1000, SCTP 1000
  parallelism: min 0, max 0
  max-retries: 10, host-timeout: 0
  min-rate: 0, max-rate: 0
---------------------------------------------
NSE: Using Lua 5.2.
NSE: Script Arguments seen from CLI:
NSE: Loaded 1 scripts for scanning.
NSE: Script Pre-scanning.
NSE: Starting runlevel 1 (of 1) scan.
mass_rdns: Using DNS server 192.168.0.1
Initiating Parallel DNS resolution of 1 host. at 07:21
mass_rdns: 0.00s 0/1 [#: 1, OK: 0, NX: 0, DR: 0, SF: 0, TR: 1]
Completed Parallel DNS resolution of 1 host. at 07:21, 0.00s elapsed
DNS resolution of 1 IPs took 0.00s. Mode: Async [#: 1, OK: 0, NX: 1, DR: 0, SF: 0, TR: 1, CN: 0]
Initiating UDP Scan at 07:21
Scanning 192.168.166.2 [1 port]
Packet capture filter (device lo): dst host 192.168.166.2 and (icmp or icmp6 or ((tcp or udp or sctp) and (src host 192.168.166.2)))
Completed UDP Scan at 07:21, 2.03s elapsed (1 total ports)
Overall sending rates: 0.98 packets / s, 27.56 bytes / s.
NSE: Script scanning 192.168.166.2.
NSE: Starting runlevel 1 (of 1) scan.
NSE: Starting dhcp-discover against 192.168.166.2:67.
Initiating NSE at 07:21
NSE: dhcp-discover against 192.168.166.2:67 threw an error!
/usr/bin/../share/nmap/nselib/dhcp.lua:449: attempt to get length of local 'mac_address' (a nil value)
stack traceback:
 /usr/bin/../share/nmap/nselib/dhcp.lua:449: in function 'dhcp_build'
 /usr/bin/../share/nmap/nselib/dhcp.lua:623: in function 'make_request'
 /usr/bin/../share/nmap/scripts/dhcp-discover.nse:108: in function 'go'
 /usr/bin/../share/nmap/scripts/dhcp-discover.nse:122: in function </usr/bin/../share/nmap/scripts/dhcp-discover.nse:121>
 (...tail calls...)

Completed NSE at 07:21, 0.00s elapsed
Nmap scan report for 192.168.166.2
Host is up, received user-set.
Scanned at 2015-07-01 07:21:45 CEST for 2s
PORT STATE SERVICE REASON
67/udp open|filtered dhcps no-response

NSE: Script Post-scanning.
NSE: Starting runlevel 1 (of 1) scan.
Read from /usr/bin/../share/nmap: nmap-payloads nmap-services.
Nmap done: 1 IP address (1 host up) scanned in 2.08 seconds
           Raw packets sent: 2 (56B) | Rcvd: 2 (56B)

expected behaviour: nmap should report some details regarding scanned dhcp server