diff --git a/hbs2-storage-ncq/lib/HBS2/Storage/NCQ3/Internal/Fsync.hs b/hbs2-storage-ncq/lib/HBS2/Storage/NCQ3/Internal/Fsync.hs
index 6dbd7765..a6a3ac35 100644
--- a/hbs2-storage-ncq/lib/HBS2/Storage/NCQ3/Internal/Fsync.hs
+++ b/hbs2-storage-ncq/lib/HBS2/Storage/NCQ3/Internal/Fsync.hs
@@ -7,17 +7,22 @@ import Foreign.C.Types
 import System.Posix.Types
 import System.Posix.Unistd (fileSynchronise)
 
-foreign import capi unsafe "unistd.h fsync"
-  c_fsync :: CInt -> IO CInt
+#ifdef darwin_HOST_OS
 
-#if defined(darwin_HOST_OS)
 foreign import capi unsafe "fcntl.h fcntl"
-  c_fcntl :: CInt -> CInt -> CInt -> IO CInt
+  c_fcntl_raw :: CInt -> CInt -> CInt -> IO CInt
 
 foreign import capi unsafe "fcntl.h value F_FULLFSYNC"
   f_FULLFSYNC :: CInt
+
+c_fcntl :: CInt -> CInt -> CInt -> IO ()
+c_fcntl fd cmd arg = do
+  _ <- c_fcntl_raw fd cmd arg
+  pure ()
+
 #endif
 
+
 fileSynchronisePortable :: Fd -> IO ()
 fileSynchronisePortable fd@(Fd fdi) = do
 #if defined(darwin_HOST_OS)