Although FilePath.validateAntFileMask is typically bounded to check at most 10000 files before giving up and announcing that it cannot find a match, it turns out that DirectoryScanner collects the names of non-matches in filesNotIncluded and dirsNotIncluded in the meantime. In a big workspace, this can cause the JVM (usually a slave agent) to allocate gigabytes of heap, eventually causing the slave to become overwhelmed and crash.