diff --git a/Nix/Parser/Library.hs b/Nix/Parser/Library.hs
index ca996e4..bad657e 100644
--- a/Nix/Parser/Library.hs
+++ b/Nix/Parser/Library.hs
@@ -83,7 +83,7 @@ import qualified Data.HashSet as HashSet
 identStyle :: IdentifierStyle Parser
 identStyle = IdentifierStyle
   { _styleName = "nix"
-  , _styleStart = letter
+  , _styleStart = letter <|> char '_'
   , _styleLetter = alphaNum <|> oneOf "_."
   , _styleReserved = HashSet.fromList reservedNames
   , _styleHighlight = Identifier