Broker logs "Error: No error" when port is unavailable

Scenario: Windows 7 64 bits, one broker up and running using the default config.

Any attempt to run a new broker using the default config logs as follows.

Alvaro@DILBERT /c/Program Files (x86)/mosquitto
$ mosquitto -v
1384330576: mosquitto version 1.2 (build date 28/08/2013 10:51:02.19) starting
1384330576: Using default config.
1384330576: Opening ipv6 listen socket on port 1883.
1384330576: Error: No error

I presume the port is being used by the first broker instance and therefore unavailable. But the log should reflect so rather than "Error: no error"