diff --git a/HStringTemplate.cabal b/HStringTemplate.cabal
--- a/HStringTemplate.cabal
+++ b/HStringTemplate.cabal
@@ -1,5 +1,5 @@
 name:                HStringTemplate
-version:             0.4.1
+version:             0.4.2
 synopsis:            StringTemplate implementation in Haskell.
 description:         A port of the Java library by Terrence Parr.
 category:            Text
diff --git a/Text/StringTemplate/Base.hs b/Text/StringTemplate/Base.hs
--- a/Text/StringTemplate/Base.hs
+++ b/Text/StringTemplate/Base.hs
@@ -145,7 +145,7 @@
 inSGen :: (STGroup a -> STGroup a) -> StringTemplate a -> StringTemplate a
 inSGen f st@STMP{senv = env} = st {senv = env {sgen = f (sgen env)} }
 
-envLookup :: (Monad m) => String -> SEnv a -> m (SElem a)
+envLookup :: String -> SEnv a -> Maybe (SElem a)
 envLookup x = M.lookup x . smp
 envInsert :: (String, SElem a) -> SEnv a -> SEnv a
 envInsert (s, x) y = y {smp = M.insert s x (smp y)}