diff --git a/lsp-test.cabal b/lsp-test.cabal
--- a/lsp-test.cabal
+++ b/lsp-test.cabal
@@ -1,5 +1,5 @@
 name:                lsp-test
-version:             0.5.0.0
+version:             0.5.0.1
 synopsis:            Functional test framework for LSP servers.
 description:
   A test framework for writing tests against 
diff --git a/src/Language/Haskell/LSP/Test/Compat.hs b/src/Language/Haskell/LSP/Test/Compat.hs
--- a/src/Language/Haskell/LSP/Test/Compat.hs
+++ b/src/Language/Haskell/LSP/Test/Compat.hs
@@ -36,7 +36,11 @@
 #if MIN_VERSION_process(1,6,3)
   getProcessID' = System.Process.getPid
 #else
+#if MIN_VERSION_process(1,6,0)
   getProcessID' (ProcessHandle mh _ _) = do
+#else
+  getProcessID' (ProcessHandle mh _) = do
+#endif
     p_ <- readMVar mh
     case p_ of
 #ifdef mingw32_HOST_OS