Error during Tutorial - Using Clover with Ant and JUnit: com.atlassian.clover.registry.NoSuchRegistryException

Following Part 1 of the demo, when I get to running the clover.report target, I get the error:
C:\Program Files\Jenkins\jobs\clovertutorial\workspace\build.xml:56: com.atlassian.clover.registry.NoSuchRegistryException: Clover registry file "C:\Program Files\Jenkins\jobs\clovertutorial\workspace\.clover\clover3_1_11.db" does not exist, cannot be read or is a directory.

The directory workspace/.clover/ is empty.

Executing the with.clover target produced a log message:
[clover-setup] Clover is enabled with initstring 'C:\Program Files\Jenkins\jobs\clovertutorial\workspace\.clover\clover3_1_11.db'

Not sure what I have to do to get the .db file created.

Any ideas?