NPE in ChecksumObserver

After Ctrl+C during 'mvn deploy' I seem to have a corrupt snapshot repository.

Subsequent deploy attempts fail with

Uploading: https://snapshots.jboss.org/maven2/org/jboss/bpm/bpm-dialect-xpdl21/1.0.0-SNAPSHOT/bpm-dialect-xpdl21-1.0.0-20080814.162232-1.jar
[INFO] Uploading project information for bpm-dialect-xpdl21 1.0.0-20080814.162232-1
[INFO] Retrieving previous metadata from snapshots.jboss.org
[INFO] ------------------------------------------------------------------------
[ERROR] FATAL ERROR
[INFO] ------------------------------------------------------------------------
[INFO] null
[INFO] ------------------------------------------------------------------------
[INFO] Trace
java.lang.NullPointerException
at org.apache.maven.wagon.observers.ChecksumObserver.transferStarted(ChecksumObserver.java:65)
at org.apache.maven.wagon.events.TransferEventSupport.fireTransferStarted(TransferEventSupport.java:100)
at org.apache.maven.wagon.AbstractWagon.fireGetStarted(AbstractWagon.java:378)
at org.apache.maven.wagon.AbstractWagon.getTransfer(AbstractWagon.java:193)
at org.apache.maven.wagon.AbstractWagon.getTransfer(AbstractWagon.java:182)
at org.apache.maven.wagon.providers.webdav.WebDavWagon.get(WebDavWagon.java:426)
at org.apache.maven.wagon.providers.webdav.WebDavWagon.get(WebDavWagon.java:377)