diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Changelog for vega-view
 
+## 0.3.1.7
+
+Bump aeson and scotty dependencies and try Yet-Another-Nix setup.
+
 ## 0.3.1.6
 
 Update to Vega Lite version 4 and drop the version requirement on
diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -34,6 +34,7 @@
 import qualified Data.HashMap.Strict as HM
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as LT
+import qualified Data.Text.Lazy.IO as LT
 import qualified Text.Blaze as B
 import qualified Text.Blaze.Html5 as H
 import qualified Text.Blaze.Html5.Attributes as A
@@ -44,7 +45,7 @@
 import Data.Aeson (Value(String, Object), Object
                   , (.=)
                   , eitherDecode', encode, object)
-import Data.List (sort)
+import Data.List (isSuffixOf, sort)
 import Data.Maybe (catMaybes)
 import Data.Version (showVersion)
 import Network.HTTP.Types (status404)
@@ -830,8 +831,8 @@
   ]
 
 
-showPage :: FilePath -> ActionM ()
-showPage infile = do
+showSpec :: FilePath -> ActionM ()
+showSpec infile = do
   espec <- liftIO (readSpec infile)
   case espec of
     Left emsg -> do
@@ -864,12 +865,20 @@
       in html (renderHtml page)
     
 
+-- This was originally only going to serve Vega-Lite specifications,
+-- but we need it to also support data files (for testing purposes,
+-- when we haven't made the data file available on GitHub). This
+-- is done in a rather hacky way: assuming the specifications
+-- always end in .vg.json.
+--
 displayPage :: FilePath -> ActionM ()
 displayPage infile = do
   isDir <- liftIO (doesDirectoryExist infile)
   if isDir
     then dirPage infile
-    else showPage infile
+    else if ".vg.json" `isSuffixOf` infile
+         then showSpec infile
+         else copyContents infile
     
 
 -- Return data needed to display this file.
@@ -883,6 +892,15 @@
                                                  , "infile" .= filename
                                                  ])
     _ -> errorStatus
+
+
+-- Not streaming, and no error handling ...
+--
+copyContents :: FilePath -> ActionM ()
+copyContents infile = do
+  cts <- liftIO $ LT.readFile infile
+  text cts
+    
 
 
 -- embed https://commons.wikimedia.org/wiki/File:Curved_Arrow.svg
diff --git a/vega-view.cabal b/vega-view.cabal
--- a/vega-view.cabal
+++ b/vega-view.cabal
@@ -1,5 +1,5 @@
 name:           vega-view
-version:        0.3.1.6
+version:        0.3.1.7
 synopsis:       Easily view Vega or Vega-Lite visualizations.
 description:    A web server that is used to view all the Vega and Vega-Lite
                 specifications in a directory, or sub-directory. It is similar
@@ -12,7 +12,7 @@
 bug-reports:    https://github.com/DougBurke/vega-view/issues
 author:         Douglas Burke
 maintainer:     dburke.gw@gmail.com
-copyright:      2019, 2020 Douglas Burke
+copyright:      2019, 2020, 2021 Douglas Burke
 license:        BSD3
 license-file:   LICENSE
 build-type:     Simple
@@ -35,7 +35,7 @@
       app
   ghc-options: -Wall -threaded -rtsopts -with-rtsopts=-N
   build-depends:
-                aeson >= 1.1 && < 1.5
+                aeson >= 1.1 && < 1.6
               , base >= 4.9 && <5
               , blaze-html >= 0.7 && < 0.10
               , blaze-markup >= 0.6 && < 0.9
@@ -43,7 +43,7 @@
               , directory >= 1.2.5.0 && < 1.4
               , filepath >= 1.4 && < 1.5
               , http-types >= 0.9 && < 0.13
-              , scotty >= 0.11 && < 0.12
+              , scotty >= 0.11 && < 0.13
               , text >= 1.2 && < 1.3
               , unordered-containers >= 0.2 && < 0.3