diff --git a/bibtex.cabal b/bibtex.cabal
--- a/bibtex.cabal
+++ b/bibtex.cabal
@@ -1,5 +1,5 @@
 Name:             bibtex
-Version:          0.1.0.5
+Version:          0.1.0.6
 License:          BSD3
 License-File:     LICENSE
 Author:           Henning Thielemann <haskell@henning-thielemann.de>
@@ -76,7 +76,7 @@
   location: http://code.haskell.org/~thielema/bibtex/
 
 Source-Repository this
-  tag:      0.1.0.5
+  tag:      0.1.0.6
   type:     darcs
   location: http://code.haskell.org/~thielema/bibtex/
 
diff --git a/src/Text/BibTeX/Parse.hs b/src/Text/BibTeX/Parse.hs
--- a/src/Text/BibTeX/Parse.hs
+++ b/src/Text/BibTeX/Parse.hs
@@ -161,7 +161,7 @@
 bibIdentifier :: Parser String
 bibIdentifier =
    lexeme $
-   liftM2 (:) (letter <|> char '_') (many (alphaNum <|> oneOf "&;:-_.?+/"))
+   liftM2 (:) (alphaNum <|> char '_') (many (alphaNum <|> oneOf "&;:-_.?+/"))
 
 
 {- |