diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,11 @@
+## 0.8.26
+
+* Add `Semigroup` instance [#123](https://github.com/snoyberg/yaml/pull/123)
+
+## 0.8.25.2
+
+* Use `throwM` instead of `monadThrow`
+
 ## 0.8.25.1
 
 * Drop aeson-qq dep (incompatible with Stackage Nightly)
diff --git a/Data/Yaml/Parser.hs b/Data/Yaml/Parser.hs
--- a/Data/Yaml/Parser.hs
+++ b/Data/Yaml/Parser.hs
@@ -9,7 +9,7 @@
 import Control.Exception (Exception)
 import Control.Monad (MonadPlus (..), liftM, ap)
 import Control.Monad.Trans.Class (lift)
-import Control.Monad.Trans.Resource (MonadThrow, monadThrow, runResourceT)
+import Control.Monad.Trans.Resource (MonadThrow, throwM, runResourceT)
 import Control.Monad.Trans.Writer.Strict (tell, WriterT)
 import Data.ByteString (ByteString)
 import Data.Conduit
@@ -18,6 +18,9 @@
 #if !MIN_VERSION_base(4,8,0)
 import Data.Monoid (Monoid (..))
 #endif
+#if !MIN_VERSION_base(4,11,0)
+import Data.Semigroup (Semigroup(..))
+#endif
 import Data.Text (Text, pack, unpack)
 import Data.Text.Encoding (decodeUtf8)
 import Data.Text.Read (signed, decimal)
@@ -36,9 +39,13 @@
 instance Alternative YamlParser where
     empty = fail "empty"
     (<|>) = mplus
+instance Semigroup (YamlParser a) where
+    (<>) = mplus
 instance Monoid (YamlParser a) where
     mempty = fail "mempty"
-    mappend = mplus
+#if !MIN_VERSION_base(4,11,0)
+    mappend = (<>)
+#endif
 instance Monad YamlParser where
     return = pure
     YamlParser f >>= g = YamlParser $ \am ->
@@ -124,7 +131,7 @@
 parseRawDoc :: (FromYaml a, MonadThrow m) => RawDoc -> m a
 parseRawDoc (RawDoc val am) =
     case unYamlParser (fromYaml val) am of
-        Left t -> monadThrow $ FromYamlException t
+        Left t -> throwM $ FromYamlException t
         Right x -> return x
 
 (.:) :: FromYaml a => [(Text, YamlValue)] -> Text -> YamlParser a
@@ -144,7 +151,7 @@
 sinkValue =
     start
   where
-    start = await >>= maybe (monadThrow UnexpectedEndOfEvents) go
+    start = await >>= maybe (throwM UnexpectedEndOfEvents) go
 
     tell' Nothing val = return val
     tell' (Just name) val = do
@@ -164,12 +171,12 @@
         let val = Mapping pairs mname
         tell' mname val
 
-    go e = monadThrow $ UnexpectedEvent e
+    go e = throwM $ UnexpectedEvent e
 
     goS front = do
         me <- await
         case me of
-            Nothing -> monadThrow UnexpectedEndOfEvents
+            Nothing -> throwM UnexpectedEndOfEvents
             Just EventSequenceEnd -> return $ front []
             Just e -> do
                 val <- go e
@@ -178,14 +185,14 @@
     goM front = do
         mk <- await
         case mk of
-            Nothing -> monadThrow UnexpectedEndOfEvents
+            Nothing -> throwM UnexpectedEndOfEvents
             Just EventMappingEnd -> return $ front []
             Just (EventScalar a b c d) -> do
                 _ <- tell' d $ Scalar a b c d
                 let k = decodeUtf8 a
                 v <- start
                 goM (front . ((k, v):))
-            Just e -> monadThrow $ UnexpectedEvent e
+            Just e -> throwM $ UnexpectedEvent e
 
 sinkRawDoc :: MonadThrow m => Consumer Event m RawDoc
 sinkRawDoc = uncurry RawDoc <$> runWriterC sinkValue
diff --git a/exe/json2yaml.hs b/exe/json2yaml.hs
--- a/exe/json2yaml.hs
+++ b/exe/json2yaml.hs
@@ -1,4 +1,3 @@
-import Control.Monad (when)
 import qualified Data.Aeson as J
 import qualified Data.ByteString as S
 import qualified Data.ByteString.Lazy as L
@@ -9,8 +8,9 @@
 main :: IO ()
 main = do
     args <- getArgs
-    when (length args > 2) $ error "Usage: json2yaml [in] [out]"
-    let (input:output:_) = args ++ repeat "-"
+    (input, output) <- case args ++ replicate (2 - length args) "-" of
+        [i, o] -> return (i, o)
+        _ -> fail "Usage: json2yaml [in] [out]"
     mval <- fmap J.decode $
         case input of
             "-" -> L.getContents
diff --git a/yaml.cabal b/yaml.cabal
--- a/yaml.cabal
+++ b/yaml.cabal
@@ -1,5 +1,5 @@
 name:            yaml
-version:         0.8.25.1
+version:         0.8.26
 license:         BSD3
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>, Anton Ageev <antage@gmail.com>,Kirill Simonov
@@ -48,8 +48,8 @@
     build-depends:   base >= 4 && < 5
                    , transformers >= 0.1
                    , bytestring >= 0.9.1.4
-                   , conduit >= 1.1.0 && < 1.3
-                   , resourcet >= 0.3 && < 1.2
+                   , conduit >= 1.1.0 && < 1.4
+                   , resourcet >= 0.3 && < 1.3
                    , aeson >= 0.7
                    , containers
                    , unordered-containers