viewer=changes emits errors indicating a failed velocity substitution

I note errors like
2009-02-24 11:35:30,793 [...XWiki/WebPreferences?viewer=changes&rev1=$%7Brev1%7D&rev2=$%7Brev2%7D] [TP-Processor7] ERROR api.XWiki - Failed to read versioned document
org.suigeneris.jrcs.rcs.InvalidVersionNumberException: ${rev1}
2009-02-24 11:35:30,795 [...XWiki/WebPreferences?viewer=changes&rev1=$%7Brev1%7D&rev2=$%7Brev2%7D] [TP-Processor7] ERROR api.XWiki - Failed to read versioned document
org.suigeneris.jrcs.rcs.InvalidVersionNumberException: ${rev2}
2009-02-24 12:10:57,801 [.../XWiki/WebPreferences?viewer=changes&rev1=$%7Brev1%7D&rev2=$%7Brev2%7D] [TP-Processor12] ERROR api.XWiki - Failed to read versioned document
org.suigeneris.jrcs.rcs.InvalidVersionNumberException: ${rev1}

in the logs after using the revision history facilities in Xwiki. To the user, things seem to work correctly, however, these errors are present in logs.