VCS trigger rule problem: exclude changes in directory

Following the examples provided, I have defined a VCS trigger rule intended to not trigger a build when changes are made to files with a directory.
This is the only trigger rule I have defined:

-:provisioning/**

Unfortunately changes to files within the provisioning directory continues to trigger builds.

No other triggers are defined for the build.

Any corrections / advice / assistance would be appreciated!

TeamCity version is 8.1 (build 29879).

Cheers,

Matthew Ueckerman