Custom rules issue

[u2john]

I wrote the rule:
[[ClassifierRules]]
EnumerationScope = "FileEnumeration"
RuleName = "EightCharAlphanumInTxt"
MatchAction = "Snaffle"
MatchLocation = "FileContentAsString"
WordListType = "Regex"
WordList = [
"(?<!\w)[a-zA-Z0-9]{8}(?!\w)"
]
Triage = "Black"
Purpose: find any file contained password, presumably with a-zA-Z0-9
I start snaffler:
.\Snaffler.exe -s -i \path\to\dir -p \path\to.toml -o output.txt
the result is:
2026-02-10 12:17:08Z [Info] Parsing args...
2026-02-10 12:17:08Z [Info] Parsed args successfully.
2026-02-10 12:17:08Z [Info] Creating a TreeWalker task for \path\to.toml
2026-02-10 12:17:08Z [Info] Created all TreeWalker tasks.
2026-02-10 12:17:08Z [Error] You've got a misconfigured file classifier rule named EightCharAlphanumInTxt.
2026-02-10 12:17:08Z [Error] You've got a misconfigured file classifier rule named EightCharAlphanumInTxt.
2026-02-10 12:17:08Z [Error] You've got a misconfigured file classifier rule named EightCharAlphanumInTxt.