diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,15 @@
 # Change Log
 
-## Version 0.0.1
+## Unreleased changes
+
+## Released changes
+
+### Version 0.0.1.1
+
+- assure proper shutdown of Java (PlantUML)
+- make call truly headless
+- use async library
+
+### Version 0.0.1
 
 - provide basic ability to call PlantUML
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# `call-plantuml` [![Haskell CI](https://github.com/marcellussiegburg/call-plantuml/workflows/Haskell%20CI/badge.svg)]
+# `call-plantuml` [![Haskell CI](https://github.com/marcellussiegburg/call-plantuml/workflows/Haskell%20CI/badge.svg)](https://github.com/marcellussiegburg/call-plantuml/workflows/Haskell%20CI/badge.svg)
 
 This is a simple library to call [PlantUML](https://plantuml.com) given a diagram specification.
 PlantUML is included (as JAR file) within this library.
diff --git a/call-plantuml.cabal b/call-plantuml.cabal
--- a/call-plantuml.cabal
+++ b/call-plantuml.cabal
@@ -1,11 +1,11 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.4.
+-- This file has been generated from package.yaml by hpack version 0.35.0.
 --
 -- see: https://github.com/sol/hpack
 
 name:           call-plantuml
-version:        0.0.1
+version:        0.0.1.1
 synopsis:       A simple library to call PlantUML given a diagram specification
 description:    Please see the README on GitHub at <https://github.com/marcellussiegburg/call-plantuml#readme>
 category:       Graphics, Language
@@ -39,14 +39,15 @@
       src
   ghc-options: -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates -Widentities -Wredundant-constraints
   build-depends:
-      base >=4.12 && <5
+      async >=2.2.1 && <2.3
+    , base >=4.12 && <5
     , bytestring >=0.10.4 && <0.12
     , filepath ==1.4.*
     , process ==1.6.*
+  default-language: Haskell2010
   if os(windows)
     cpp-options: -DWINDOWS
   else
-  default-language: Haskell2010
 
 test-suite call-plantuml-test
   type: exitcode-stdio-1.0
@@ -58,13 +59,14 @@
       test
   ghc-options: -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates -Widentities -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
   build-depends:
-      base >=4.12 && <5
+      async >=2.2.1 && <2.3
+    , base >=4.12 && <5
     , bytestring >=0.10.4 && <0.12
     , call-plantuml
     , filepath ==1.4.*
     , hspec
     , process ==1.6.*
+  default-language: Haskell2010
   if os(windows)
     cpp-options: -DWINDOWS
   else
-  default-language: Haskell2010
diff --git a/src/Language/PlantUML/Call.hs b/src/Language/PlantUML/Call.hs
--- a/src/Language/PlantUML/Call.hs
+++ b/src/Language/PlantUML/Call.hs
@@ -12,6 +12,7 @@
 -}
 module Language.PlantUML.Call (
   DiagramType (..),
+  drawPlantUmlDiagram,
   drawPlantUMLDiagram,
   ) where
 
@@ -25,9 +26,8 @@
   tail,
   )
 
-import Control.Concurrent (
-  forkIO, killThread, newEmptyMVar, putMVar, takeMVar,
-  )
+import Control.Concurrent.Async         (concurrently)
+import Control.Exception                (bracket)
 import Control.Monad                    (unless, when)
 import Data.ByteString                  (ByteString, hGetContents, hPutStr)
 import Data.ByteString.Char8            (unpack)
@@ -35,6 +35,7 @@
 import System.FilePath
   ((</>), (<.>))
 import System.IO (
+  Handle,
   hClose,
   hFlush,
 #ifndef mingw32_HOST_OS
@@ -43,8 +44,13 @@
 #endif
   )
 import System.Process (
-  CreateProcess (..), StdStream (..),
-  createProcess, proc, waitForProcess,
+  CreateProcess (..),
+  ProcessHandle,
+  StdStream (..),
+  cleanupProcess,
+  createProcess,
+  proc,
+  waitForProcess,
   )
 
 {-|
@@ -73,54 +79,64 @@
   VDX               -> "vdx"
 
 {-|
+Calls PlantUml (Java) using the given 'DiagramType'.
+Assures proper closing of the processes.
+-}
+callPlantUml
+  :: DiagramType
+  -> ((Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> IO a)
+  -> IO a
+callPlantUml what = flip bracket cleanupProcess $ do
+  dataDir <- getDataDir
+  let callPlantUML = proc "java" [
+        "-Djava.awt.headless=true",
+        "-jar", dataDir </> "plantuml" <.> "jar",
+        "-p", "-t" ++ typeShortName what, "-nometadata", "-noerror"
+        ]
+  createProcess callPlantUML {
+    std_out = CreatePipe,
+    std_in  = CreatePipe,
+    std_err = CreatePipe
+    }
+
+{-|
+A synonym for 'drawPlantUmlDiagram'.
+-}
+drawPlantUMLDiagram :: DiagramType -> ByteString -> IO ByteString
+drawPlantUMLDiagram = drawPlantUmlDiagram
+
+{-|
 This function may be used to draw a PlantUML diagram given a valid
 specification and a return type.
 It calls PlantUML via Java.
 -}
-drawPlantUMLDiagram
+drawPlantUmlDiagram
   :: DiagramType
   -- ^ The return type of diagram to return
   -> ByteString
   -- ^ The PlantUML diagram specification which should be loaded
   -> IO ByteString
-drawPlantUMLDiagram what content = do
-  dataDir <- getDataDir
-  let callPlantUML = proc "java" [
-        "-jar", dataDir </> "plantuml" <.> "jar",
-        "-p", "-t" ++ typeShortName what, "-nometadata", "-noerror"
-        ]
-  (Just hin, Just hout, Just herr, ph) <-
-    createProcess callPlantUML {
-        std_out = CreatePipe,
-        std_in  = CreatePipe,
-        std_err = CreatePipe
-      }
-  pout <- listenForOutput hout
-  perr <- listenForOutput herr
+drawPlantUmlDiagram what content = callPlantUml what $ \p -> do
+  (Just hin, Just hout, Just herr, ph) <- return p
 #ifndef mingw32_HOST_OS
   hSetBuffering hin NoBuffering
 #endif
-  hPutStr hin content
-  hFlush hin
-  hClose hin
-  out <- getOutput pout
-  err <- getOutput perr
+  let evaluatePlantUml = do
+        hPutStr hin content
+        hFlush hin
+        hClose hin
+        waitForProcess ph
+  (out, err) <- fst <$> concurrently
+    (concurrently (hGetContents hout) (hGetContents herr))
+    evaluatePlantUml
   printContentOnError ph out
   unless (BS.null err) $ fail $ unpack err
   return out
   where
     printContentOnError ph out = do
       code <- waitForProcess ph
-      when (code == ExitFailure 1 || isError out)
+      when (code /= ExitSuccess || isError out)
         $ BS.putStrLn $ "Error on calling PlantUML with:\n" <> content
-    listenForOutput h = do
-      mvar <- newEmptyMVar
-      pid <- forkIO $ hGetContents h >>= putMVar mvar
-      return (pid, mvar)
-    getOutput (pid, mvar) = do
-      output <- takeMVar mvar
-      killThread pid
-      return output
 
 isError :: ByteString -> Bool
 isError xs =