diff --git a/Application.hs b/Application.hs
index 8b235bc..c8bcec5 100644
--- a/Application.hs
+++ b/Application.hs
@@ -134,7 +134,7 @@ makeFoundation conf = do
                 runDB' = runResourceT . flip (Database.Persist.runPool dbconf) p
             uploadHistory0 <- runDB' $ selectSource [] [] $$ sinkUploadHistory
             UploadState uploadHistory newUploads <- loadCabalFiles uploadHistory0
-            runDB' $ mapM_ insert newUploads
+            runDB' $ mapM_ insert_ newUploads
             let views =
                     [ ("pvp", viewPVP uploadHistory)
                     , ("no-bounds", viewNoBounds)
diff --git a/Handler/Aliases.hs b/Handler/Aliases.hs
index 11583e8..bf4a9f3 100644
--- a/Handler/Aliases.hs
+++ b/Handler/Aliases.hs
@@ -10,7 +10,7 @@ putAliasesR = do
     aliases <- mapM (parseAlias uid) $ lines aliasesText
     runDB $ do
         deleteWhere [AliasUser ==. uid]
-        mapM_ insert aliases
+        mapM_ insert_ aliases
     setMessage "Aliases updated"
     redirect ProfileR
 
diff --git a/Handler/UploadStackage.hs b/Handler/UploadStackage.hs
index 715cc4a..3f63b2e 100644
--- a/Handler/UploadStackage.hs
+++ b/Handler/UploadStackage.hs
@@ -18,6 +18,8 @@ import Control.Monad.State.Strict (execStateT, get, put)
 import qualified Codec.Compression.GZip as GZip
 import Control.Monad.Trans.Resource (unprotect, allocate)
 import System.Directory (removeFile, getTemporaryDirectory)
+import System.Process (runProcess, waitForProcess)
+import System.Exit (ExitCode (ExitSuccess))
 
 fileKey :: Text
 fileKey = "stackage"
@@ -81,12 +83,22 @@ putUploadStackageR = do
                         , lsFiles = mempty
                         , lsIdent = ident
                         }
-                    entries <- liftIO $ Tar.pack dir $ map fpToString $ setToList files
-                    let indexLBS = GZip.compress $ Tar.write entries
-                    sourceLazy indexLBS $$ storeWrite (CabalIndex ident)
-                    runDB $ insert stackage
+                    withSystemTempFile "newindex" $ \fp h -> do
+                        ec <- liftIO $ do
+                            hClose h
+                            let args = "cfz"
+                                     : fp
+                                     : map fpToString (setToList files)
+                            ph <- runProcess "tar" args (Just dir) Nothing Nothing Nothing Nothing
+                            waitForProcess ph
+                        if ec == ExitSuccess
+                            then do
+                                sourceFile (fpFromString fp) $$ storeWrite (CabalIndex ident)
+                                runDB $ insert stackage
 
-                    done "Stackage created" $ StackageHomeR ident
+                                done "Stackage created" $ StackageHomeR ident
+                            else do
+                                done "Error creating index file" ProfileR
 
             redirect $ ProgressR key
   where
diff --git a/stackage-server.cabal b/stackage-server.cabal
index 0e32bca..23e93a3 100644
--- a/stackage-server.cabal
+++ b/stackage-server.cabal
@@ -93,7 +93,7 @@ library
                  , fast-logger                   >= 2.1.4      && < 2.2
                  , wai                           >= 2.1        && < 2.2
                  , wai-logger                    >= 2.1        && < 2.2
-                 , classy-prelude-yesod          >= 0.9        && < 0.9.1
+                 , classy-prelude-yesod          >= 0.9.2      && < 0.9.3
                  , mwc-random                    >= 0.13       && < 0.14
                  , mtl                           >= 2.1        && < 2.2
                  , blaze-markup                  >= 0.6        && < 0.7
@@ -119,6 +119,7 @@ library
                  , lifted-base
                  , mono-traversable
                  , time
+                 , process
 
 executable         stackage-server
     if flag(library-only)