diff --git a/solga/src/Solga.hs b/solga/src/Solga.hs
index 43f212a..d929e3d 100644
--- a/solga/src/Solga.hs
+++ b/solga/src/Solga.hs
@@ -283,7 +283,7 @@ class Abbreviated a where
   type Brief a :: *
   type instance Brief a = a
   brief :: Brief a -> a
-  default brief :: a -> a
+  default brief :: Brief a ~ a => Brief a -> a
   brief = id
 
 instance Abbreviated Raw where
diff --git a/solga/test/Test.hs b/solga/test/Test.hs
index 4ed30aa..331a901 100644
--- a/solga/test/Test.hs
+++ b/solga/test/Test.hs
@@ -93,7 +93,6 @@ spec = with (return $ serve testAPI) $ do
       resp <- get path
       liftIO $ decode (simpleBody resp) `shouldBe` Just (String seg)
 
-deriving instance Generic Value
 
 instance Arbitrary Value where
   arbitrary = sized arbJSON
@@ -133,4 +132,4 @@ instance Arbitrary a => Arbitrary (V.Vector a) where
 
 instance Arbitrary S.Scientific where
   arbitrary = S.scientific <$> arbitrary <*> arbitrary
-  shrink s = map (uncurry S.scientific) $ shrink $ ( S.coefficient s, S.base10Exponent s )
\ No newline at end of file
+  shrink s = map (uncurry S.scientific) $ shrink $ ( S.coefficient s, S.base10Exponent s )
diff --git a/stack.yaml b/stack.yaml
index 69ac7ac..df0223f 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,7 +1,7 @@
 # For more information, see: https://github.com/commercialhaskell/stack/blob/release/doc/yaml_configuration.md
 
 # Specifies the GHC version and set of packages available (e.g., lts-3.5, nightly-2015-09-21, ghc-7.10.2)
-resolver: nightly-2016-11-07
+resolver: nightly-2017-07-31
 
 # Local packages, usually specified by relative directory name
 packages:
@@ -10,7 +10,8 @@ packages:
 
 # Packages to be pulled from upstream that are not in the resolver (e.g., acme-missiles-0.3)
 extra-deps:
-- safe-exceptions-0.1.1.0
+- swagger2-2.1.4.1
+- http-media-0.7.1.1
 
 # Override default flag values for local packages and extra-deps
 flags: {}