diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -4,6 +4,10 @@
 
 ## Released changes
 
+### 0.2.1.0
+
+- enable to abort instance generation early by using timeout
+
 ### 0.2.0.6
 
 - allow parsing `'` as part of words.
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: 17a876c2f193cdf8cf992b6455dab5e37d246e48f9988f98f1c8e38d374e6dd0
+-- hash: db841f71ac1e6d568aa7c8d4f6574b06cdf77fea00a6cf3ae0c74880c12eb083
 
 name:           call-alloy
-version:        0.2.0.6
+version:        0.2.1.0
 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
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
@@ -1,3 +1,4 @@
+{-# LANGUAGE ScopedTypeVariables #-}
 {-|
 Module      : Language.Alloy.Call
 Description : A simple library to call Alloy given a specification
@@ -14,7 +15,7 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE OverloadedStrings #-}
 module Language.Alloy.Call (
-  CallAlloyConfig (maxInstances, noOverflow),
+  CallAlloyConfig (maxInstances, noOverflow, timeout),
   defaultCallAlloyConfig,
   existsInstance,
   getInstances,
@@ -24,13 +25,16 @@
   ) where
 
 import qualified Data.ByteString                  as BS
-  (hGetLine, intercalate, writeFile)
+  (hGetLine, intercalate, isSuffixOf, writeFile)
 import qualified Data.ByteString.Char8            as BS (unlines)
 
-import Control.Concurrent
-  (forkIO, killThread, newEmptyMVar, putMVar, takeMVar)
+import Control.Concurrent (
+  ThreadId,
+  forkIO, killThread, newEmptyMVar, putMVar, takeMVar, threadDelay,
+  )
+import Control.Exception                (IOException)
 import Control.Lens.Internal.ByteString (unpackStrict8)
-import Control.Monad                    (unless)
+import Control.Monad                    (unless, void, when)
 import Data.ByteString                  (ByteString)
 import Data.Hashable                    (hash)
 import Data.IORef                       (IORef, newIORef, readIORef)
@@ -46,10 +50,12 @@
 import System.FilePath
   ((</>), (<.>), searchPathSeparator, takeDirectory)
 import System.IO
-  (BufferMode (..), hClose, hFlush, hIsEOF, hPutStr, hSetBuffering)
+  (BufferMode (..), Handle, hClose, hFlush, hIsEOF, hPutStr, hSetBuffering)
 import System.IO.Unsafe                 (unsafePerformIO)
-import System.Process
-  (CreateProcess (..), StdStream (..), createProcess, proc, waitForProcess)
+import System.Process (
+  CreateProcess (..), StdStream (..), ProcessHandle,
+  createProcess, proc, terminateProcess, waitForProcess,
+  )
 #if defined(mingw32_HOST_OS)
 import System.Win32.Info                (getUserName)
 #else
@@ -70,12 +76,17 @@
 
  * maximal number of instances to retrieve ('Nothing' for all)
  * wheather to not overflow when calculating numbers within Alloy
+ * an timeout after which to forcibly kill Alloy
+   (retrieving only instances that were returned before killing the process)
 -}
 data CallAlloyConfig = CallAlloyConfig {
   -- | maximal number of instances to retrieve ('Nothing' for all)
   maxInstances :: Maybe Integer,
   -- | wheather to not overflow when calculating numbers within Alloy
-  noOverflow   :: Bool
+  noOverflow   :: Bool,
+  -- | the time in microseconds after which to forcibly kill Alloy
+  --   ('Nothing' for never)
+  timeout      :: Maybe Int
   }
 
 {-|
@@ -87,7 +98,8 @@
 defaultCallAlloyConfig :: CallAlloyConfig
 defaultCallAlloyConfig = CallAlloyConfig {
   maxInstances = Nothing,
-  noOverflow   = True
+  noOverflow   = True,
+  timeout      = Nothing
   }
 
 {-# NOINLINE mclassPath #-}
@@ -138,6 +150,7 @@
       }
   pout <- listenForOutput hout
   perr <- listenForOutput herr
+  maybe (return ()) (void . startTimeout hin hout herr ph) $ timeout config
 #ifndef mingw32_HOST_OS
   hSetBuffering hin NoBuffering
 #endif
@@ -149,18 +162,26 @@
   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
+  let finstas = filterLast (not . (partialInstance `BS.isSuffixOf`)) instas
+  return $ either (error . show) id . parseInstance <$> finstas
   where
     begin :: ByteString
     begin = "---INSTANCE---"
+    partialInstance :: ByteString
+    partialInstance = "---PARTIAL_INSTANCE---"
+    filterLast _ []     = []
+    filterLast p x@[_]  = filter p x
+    filterLast p (x:xs) = x:filterLast p xs
     getWholeOutput h = do
       eof <- hIsEOF h
       if eof
         then return []
-        else (:) <$> BS.hGetLine h <*> getWholeOutput h
+      else catch
+        ((:) <$> BS.hGetLine h <*> getWholeOutput h)
+        (\(_ :: IOException) -> return [partialInstance])
     printContentOnError ph = do
       code <- waitForProcess ph
-      unless (code == ExitSuccess)
+      when (code == ExitFailure 1)
         $ putStrLn $ "Failed parsing the Alloy code:\n" <> content
     listenForOutput h = do
       mvar <- newEmptyMVar
@@ -170,6 +191,27 @@
       output <- takeMVar mvar
       killThread pid
       return output
+
+{-|
+Start a new process that aborts execution by closing all handles and
+killing the processes after the given amount of time.
+-}
+startTimeout
+  :: Handle
+  -- ^ the input handle to close
+  -> Handle
+  -- ^ the output handle to close
+  -> Handle
+  -- ^ the error handle to close
+  -> ProcessHandle
+  -- ^ the main process handle
+  -> Int -> IO ThreadId
+startTimeout i o e ph t = forkIO $ do
+  threadDelay t
+  void $ forkIO $ hClose e
+  void $ forkIO $ hClose o
+  terminateProcess ph
+  hClose i
 
 {-|
 Check if the class path was determined already, if so use it, otherwise call
diff --git a/test/Language/Alloy/CallSpec.hs b/test/Language/Alloy/CallSpec.hs
--- a/test/Language/Alloy/CallSpec.hs
+++ b/test/Language/Alloy/CallSpec.hs
@@ -10,6 +10,7 @@
 import Language.Alloy.Call              (existsInstance, getInstances)
 import Language.Alloy.Types             (Entry (..), Relation (..))
 
+import Language.Alloy.Call              (getInstancesWith, defaultCallAlloyConfig, CallAlloyConfig (..))
 deriving instance Eq (Relation Set)
 deriving instance Eq (Entry Map Set)
 
@@ -28,3 +29,5 @@
       (show <$> getInstances (Just 2) "") `shouldReturn` "[fromList [(Signature {scope = Nothing, sigName = \"Int\"},Entry {annotation = Nothing, relation = fromList [(\"\",Single (fromList [NumberObject {number = -8},NumberObject {number = -7},NumberObject {number = -6},NumberObject {number = -5},NumberObject {number = -4},NumberObject {number = -3},NumberObject {number = -2},NumberObject {number = -1},NumberObject {number = 0},NumberObject {number = 1},NumberObject {number = 2},NumberObject {number = 3},NumberObject {number = 4},NumberObject {number = 5},NumberObject {number = 6},NumberObject {number = 7}]))]}),(Signature {scope = Nothing, sigName = \"String\"},Entry {annotation = Nothing, relation = fromList [(\"\",EmptyRelation)]}),(Signature {scope = Nothing, sigName = \"integers\"},Entry {annotation = Nothing, relation = fromList [(\"\",Single (fromList [NumberObject {number = -8},NumberObject {number = -7},NumberObject {number = -6},NumberObject {number = -5},NumberObject {number = -4},NumberObject {number = -3},NumberObject {number = -2},NumberObject {number = -1},NumberObject {number = 0},NumberObject {number = 1},NumberObject {number = 2},NumberObject {number = 3},NumberObject {number = 4},NumberObject {number = 5},NumberObject {number = 6},NumberObject {number = 7}]))]}),(Signature {scope = Nothing, sigName = \"none\"},Entry {annotation = Nothing, relation = fromList [(\"\",EmptyRelation)]}),(Signature {scope = Nothing, sigName = \"univ\"},Entry {annotation = Nothing, relation = fromList [(\"\",Single (fromList [NumberObject {number = -8},NumberObject {number = -7},NumberObject {number = -6},NumberObject {number = -5},NumberObject {number = -4},NumberObject {number = -3},NumberObject {number = -2},NumberObject {number = -1},NumberObject {number = 0},NumberObject {number = 1},NumberObject {number = 2},NumberObject {number = 3},NumberObject {number = 4},NumberObject {number = 5},NumberObject {number = 6},NumberObject {number = 7}]))]}),(Signature {scope = Just \"seq\", sigName = \"Int\"},Entry {annotation = Nothing, relation = fromList [(\"\",Single (fromList [NumberObject {number = 0},NumberObject {number = 1},NumberObject {number = 2},NumberObject {number = 3}]))]})]]"
     it "a conflicting spec returns no instance" $
       getInstances (Just 1) "pred a (a: Int) { a > a }\nrun a" `shouldReturn` []
+    it "a conflicting spec returns error" $
+      getInstancesWith defaultCallAlloyConfig {maxInstances = Just 1, timeout = Just 1} "pred a (a: Int) { a > a }\nrun a" `shouldReturn` []