diff --git a/System/Linux/FileExtents.hsc b/System/Linux/FileExtents.hsc
--- a/System/Linux/FileExtents.hsc
+++ b/System/Linux/FileExtents.hsc
@@ -7,7 +7,7 @@
 --
 -- This module can be used to retrieve information about how a
 -- particular file is stored on disk (i.e. the file fragmentation).
--- It accomplishes that by directly calling the FIEMAP ioctl provided by
+-- It accomplishes that by calling the FIEMAP ioctl provided by
 -- recent versions of the Linux kernel. This ioctl is specific to Linux
 -- and therefore this module is not portable.
 --
@@ -119,9 +119,13 @@
     }
   deriving (Show, Eq)
 
+#if __GLASGOW_HASKELL__ < 800
+#let alignment t = "%lu", (unsigned long)offsetof(struct {char x__; t (y__); }, y__)
+#endif
+
 instance Storable Extent where
     sizeOf _ = #size struct fiemap_extent
-    alignment _ = alignment (undefined :: Int)
+    alignment _ = (#alignment struct fiemap_extent)
     peek ptr = do
         extLogical_  <- (#peek struct fiemap_extent, fe_logical ) ptr
         extPhysical_ <- (#peek struct fiemap_extent, fe_physical) ptr
@@ -138,7 +142,7 @@
 --------------------------------------------------------------------------------
 -- request flags
 
--- |Flags the modify the behavior of extent information requests.
+-- |Flags that modify the behavior of extent information requests.
 data ReqFlags = ReqFlags
     { rfSync :: Bool  -- ^ Sync the file before requesting its extents.
     , rfXattr :: Bool -- ^ Retrieve the extents of the inode's extended attribute lookup tree, instead of its data tree.
@@ -182,7 +186,7 @@
 -- file descriptors.
 getExtents :: ReqFlags -> FilePath -> Maybe (Word64, Word64) -> IO [Extent]
 getExtents flags path range =
-    bracket (openFd path ReadOnly Nothing defaultFileFlags) closeFd $ \fd ->
+    bracket (openFd path ReadOnly defaultFileFlags) closeFd $ \fd ->
         getExtentsPathFd "getExtents" (Just path) flags fd range
 
 getExtentsPathFd :: String -> Maybe FilePath -> ReqFlags -> Fd -> Maybe (Word64, Word64) -> IO [Extent]
@@ -228,7 +232,7 @@
 -- instead of a list.
 getExtentCount :: ReqFlags -> FilePath -> Maybe (Word64, Word64) -> IO Word32
 getExtentCount flags path range =
-    bracket (openFd path ReadOnly Nothing defaultFileFlags) closeFd $ \fd ->
+    bracket (openFd path ReadOnly defaultFileFlags) closeFd $ \fd ->
         getExtentCountPathFd "getExtentCount" (Just path) flags fd range
 
 getExtentCountPathFd :: String -> Maybe FilePath -> ReqFlags -> Fd -> Maybe (Word64, Word64) -> IO Word32
diff --git a/linux-file-extents.cabal b/linux-file-extents.cabal
--- a/linux-file-extents.cabal
+++ b/linux-file-extents.cabal
@@ -1,5 +1,5 @@
 name:                linux-file-extents
-version:             0.2.0.0
+version:             0.2.0.1
 synopsis:            Retrieve file fragmentation information under Linux
 description:
   This package provides a simple wrapper around the Linux FIEMAP ioctl.
@@ -31,7 +31,7 @@
 library
   exposed-modules:     System.Linux.FileExtents
   include-dirs:        include
-  build-depends:       base >=4.6 && <5, unix >=2.6
+  build-depends:       base >=4.6 && <5, unix >=2.8
   build-tools:         hsc2hs
   default-language:    Haskell2010
   ghc-options:         -Wall