diff --git a/salak-yaml.cabal b/salak-yaml.cabal
--- a/salak-yaml.cabal
+++ b/salak-yaml.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.12
 name: salak-yaml
-version: 0.2.9
+version: 0.2.9.1
 license: BSD3
 license-file: LICENSE
 copyright: (c) 2018 Daniel YU
@@ -27,7 +27,7 @@
         conduit >=1.3.1.1 && <1.4,
         libyaml >=0.1.1.0 && <0.2,
         mtl >=2.2.2 && <2.3,
-        salak ==0.2.9,
+        salak ==0.2.9.*,
         text >=1.2.3.1 && <1.3
 
 test-suite spec
@@ -46,5 +46,5 @@
         hspec ==2.*,
         libyaml >=0.1.1.0 && <0.2,
         mtl >=2.2.2 && <2.3,
-        salak ==0.2.9,
+        salak ==0.2.9.*,
         text >=1.2.3.1 && <1.3
diff --git a/src/Salak/Yaml.hs b/src/Salak/Yaml.hs
--- a/src/Salak/Yaml.hs
+++ b/src/Salak/Yaml.hs
@@ -1,6 +1,16 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE RecordWildCards  #-}
 {-# LANGUAGE TupleSections    #-}
+-- |
+-- Module:      Salak.Yaml
+-- Copyright:   (c) 2019 Daniel YU
+-- License:     BSD3
+-- Maintainer:  leptonyu@gmail.com
+-- Stability:   experimental
+-- Portability: portable
+--
+-- Yaml support for "Salak". Yaml alias and anchor is not supported.
+--
 module Salak.Yaml(
     YAML(..)
   , loadYaml
@@ -14,9 +24,11 @@
 import           Salak.Load
 import           Text.Libyaml
 
+-- | Load Yaml
 loadYaml :: MonadIO m => FilePath -> LoadSalakT m ()
 loadYaml file = loadFile file $ \i s -> liftIO $ runConduitRes (decodeFileMarked file .| loadYAML i s)
 
+-- | YAML notation for `loadYaml`
 data YAML = YAML
 
 instance HasLoad YAML where
@@ -29,6 +41,7 @@
     go (MarkedEvent EventSequenceStart{}  _ _) = goSeq 0 s
     go (MarkedEvent EventSequenceEnd      _ _) = return emptySource
     go (MarkedEvent EventMappingStart{}  _ ee) = goMap ee s
+    go (MarkedEvent (EventAlias a)       _ ee) = ge ee $ "alias " ++ a ++ " not supported by salak"
     go _ = loadYAML i s
     goSeq j s1 = do
       s' <- loadYAML i emptySource
@@ -42,7 +55,7 @@
         Just (MarkedEvent (EventScalar a _ _ _) _ ee') ->
           updateSources (simpleSelectors $ decodeUtf8 a) (loadYAML i) s1 >>= goMap ee'
         Just (MarkedEvent EventMappingEnd _ _) -> return s1
-        Just e -> ge (yamlStartMark e) "suppose scalar and mapping end"
+        Just e -> ge (yamlStartMark e) ("suppose scalar and mapping end, but is " ++ show (yamlEvent e))
     ge YamlMark{..} e = liftIO $ throwIO $ YamlException $ "(" ++ show yamlLine ++ "," ++ show yamlColumn ++ ")" ++ e
 
 
diff --git a/test/Spec.hs b/test/Spec.hs
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -15,6 +15,7 @@
 import           Test.Hspec
 import           Test.QuickCheck
 
+main :: IO ()
 main = hspec spec
 
 spec :: Spec
@@ -50,6 +51,7 @@
 
 instance FromProp Conf
 
+jsonProperty :: SpecWith ()
 jsonProperty = do
   context "load json" $ do
     it "salak.yml" $ do