diff --git a/classify.cabal b/classify.cabal
--- a/classify.cabal
+++ b/classify.cabal
@@ -1,5 +1,5 @@
 Name:           classify
-Version:        2008.10.20.1
+Version:        2008.11.13
 Copyright:      2004-2008, Lemmih
 Build-Depends:  base, mtl, containers
 Build-Type:     Simple
diff --git a/src/Data/Classify/Parser.hs b/src/Data/Classify/Parser.hs
--- a/src/Data/Classify/Parser.hs
+++ b/src/Data/Classify/Parser.hs
@@ -113,7 +113,9 @@
 parseSeries known
     = do many anyChar
          nPre <- many1 anyChar
-         n <- Map.lookup (trunc nPre) known
+         n <- case Map.lookup (trunc nPre) known of
+                Nothing -> fail "not known"
+                Just v  -> return v
 --         guard (trunc n `Map.member` known)
          s <- look
          guard (take 2 s /= "th") -- Fix for '24th 2007.avi'. It shouldn't parse 24th as a series.