diff --git a/bin/alloy/RunAlloy.class b/bin/alloy/RunAlloy.class
Binary files a/bin/alloy/RunAlloy.class and b/bin/alloy/RunAlloy.class differ
diff --git a/call-alloy.cabal b/call-alloy.cabal
--- a/call-alloy.cabal
+++ b/call-alloy.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: dd057700e60aba8aee8cf2105303394e8c7934479b6057c438b6a3c423f514b4
+-- hash: 5f40f17f800e12b3cb98ac3b1383ac04a52cd1570b5329b12f3fffb03bdf46ab
 
 name:           call-alloy
-version:        0.2.0.1
+version:        0.2.0.3
 synopsis:       A simple library to call Alloy given a specification
 description:    Please see the README on GitHub at <https://github.com/marcellussiegburg/call-alloy#readme>
 category:       Language
@@ -55,14 +55,13 @@
     , process >=1.6 && <1.7
     , split >=0.2 && <0.3
     , trifecta >=2 && <2.2
-    , unix >=2.7 && <2.8
   if os(windows)
     cpp-options: -DWINDOWS
     build-depends:
         Win32
   else
     build-depends:
-        unix
+        unix >=2.7 && <2.8
   default-language: Haskell2010
 
 test-suite call-alloy-test
@@ -96,12 +95,11 @@
     , process >=1.6 && <1.7
     , split >=0.2 && <0.3
     , trifecta >=2 && <2.2
-    , unix >=2.7 && <2.8
   if os(windows)
     cpp-options: -DWINDOWS
     build-depends:
         Win32
   else
     build-depends:
-        unix
+        unix >=2.7 && <2.8
   default-language: Haskell2010
diff --git a/src/Language/Alloy/Call.hs b/src/Language/Alloy/Call.hs
--- a/src/Language/Alloy/Call.hs
+++ b/src/Language/Alloy/Call.hs
@@ -22,27 +22,31 @@
 
 import qualified Data.ByteString                  as BS
   (hGetLine, intercalate, writeFile)
+import qualified Data.ByteString.Char8            as BS (unlines)
 
-import Control.Monad                    (unless)
+import Control.Concurrent
+  (forkIO, killThread, newEmptyMVar, putMVar, takeMVar)
 import Control.Lens.Internal.ByteString (unpackStrict8)
+import Control.Monad                    (unless)
 import Data.ByteString                  (ByteString)
 import Data.Hashable                    (hash)
 import Data.IORef                       (IORef, newIORef, readIORef)
 import Data.List.Split                  (splitOn)
-import Data.Maybe                       (fromMaybe, isJust)
+import Data.Maybe                       (fromMaybe)
 import System.Directory
   (XdgDirectory (..), createDirectory, doesFileExist, doesDirectoryExist,
    getTemporaryDirectory, getXdgDirectory)
 import System.Directory.Internal        (setFileMode)
 import System.Directory.Internal.Prelude
   (catch, isDoesNotExistError)
-import System.Environment               (lookupEnv)
 import System.Exit                      (ExitCode (..))
 import System.FilePath
   ((</>), (<.>), searchPathSeparator, takeDirectory)
-import System.IO                        (hClose, hIsEOF, hPutStr)
+import System.IO
+  (BufferMode (..), hClose, hFlush, hIsEOF, hPutStr, hSetBuffering)
 import System.IO.Unsafe                 (unsafePerformIO)
 import System.Process
+  (CreateProcess (..), StdStream (..), createProcess, proc, waitForProcess)
 #if defined(mingw32_HOST_OS)
 import System.Win32.Info                (getUserName)
 #else
@@ -71,8 +75,8 @@
 
 {-|
 This function may be used to get all model instances for a given Alloy
-specification. It calls Alloy via a Java interface and returns the raw instance
-answers as list of 'String's.
+specification. It calls Alloy via a Java interface and parses the raw instance
+answers before returning the resulting list of 'AlloyInstance's.
 -}
 getInstances
   :: Maybe Integer
@@ -91,11 +95,17 @@
         std_in  = CreatePipe,
         std_err = CreatePipe
       }
+  pout <- listenForOutput hout
+  perr <- listenForOutput herr
+  hSetBuffering hin NoBuffering
   hPutStr hin content
+  hFlush hin
   hClose hin
-  printCallErrors herr
-  instas <- printContentOnError ph `seq`
-    fmap (BS.intercalate "\n") . drop 1 . splitOn [begin] <$> getWholeOutput hout
+  out <- getOutput pout
+  err <- getOutput perr
+  printContentOnError ph
+  unless (null err) $ fail $ unpackStrict8 $ BS.unlines err
+  let instas = fmap (BS.intercalate "\n") $ drop 1 $ splitOn [begin] out
   return $ either (error . show) id . parseInstance <$> instas
   where
     begin :: ByteString
@@ -108,10 +118,15 @@
     printContentOnError ph = do
       code <- waitForProcess ph
       unless (code == ExitSuccess)
-        $ fail $ "Failed parsing your file:\n" <> content
-    printCallErrors err = do
-      errors <- getWholeOutput err
-      unless (null errors) $ fail $ unpackStrict8 $ BS.intercalate "\n" errors
+        $ fail $ "Failed parsing the Alloy code:\n" <> content
+    listenForOutput h = do
+      mvar <- newEmptyMVar
+      pid <- forkIO $ getWholeOutput h >>= putMVar mvar
+      return (pid, mvar)
+    getOutput (pid, mvar) = do
+      output <- takeMVar mvar
+      killThread pid
+      return output
 
 {-|
 Check if the class path was determined already, if so use it, otherwise call