diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+0.4.1
+---
+* Fixes:
+    * Use `PackageImports` for `Data.HashSet` to avoid test failure on stackage (see [#15](https://github.com/GetShopTV/swagger2/issues/15));
+    * Add an upper version bound for `aeson` due to `aeson-0.10.0.0` bug (see [bos/aeson#293](https://github.com/bos/aeson/issues/293));
+    * Switch to Cabal-based multi GHC Travis config.
+
 0.4
 ---
 * Remove `Swagger`/`swagger` prefixes;
diff --git a/src/Data/Swagger/Schema/Internal.hs b/src/Data/Swagger/Schema/Internal.hs
--- a/src/Data/Swagger/Schema/Internal.hs
+++ b/src/Data/Swagger/Schema/Internal.hs
@@ -3,6 +3,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PackageImports #-}
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TupleSections #-}
@@ -15,7 +16,7 @@
 import Data.Aeson
 import Data.Char
 import Data.HashMap.Strict (HashMap)
-import Data.HashSet (HashSet)
+import "unordered-containers" Data.HashSet (HashSet)
 import Data.Int
 import Data.IntSet (IntSet)
 import Data.IntMap (IntMap)
diff --git a/swagger2.cabal b/swagger2.cabal
--- a/swagger2.cabal
+++ b/swagger2.cabal
@@ -1,5 +1,5 @@
 name:                swagger2
-version:             0.4
+version:             0.4.1
 synopsis:            Swagger 2.0 data model
 description:         Please see README.md
 homepage:            https://github.com/GetShopTV/swagger2
@@ -28,7 +28,7 @@
     Data.Swagger.Internal.Utils
     Data.Swagger.Schema.Internal
   build-depends:       base == 4.*
-                     , aeson
+                     , aeson < 0.10
                      , containers
                      , hashable
                      , http-media