diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,3 +1,7 @@
+### 0.3.1.0
+
+- added versioning support to test for compatibility in C code.
+
 ### 0.3.0.0
 
 - added an asynchronous client request body handler exported with
diff --git a/NgxExport.hs b/NgxExport.hs
--- a/NgxExport.hs
+++ b/NgxExport.hs
@@ -1,4 +1,5 @@
-{-# LANGUAGE TemplateHaskell, ViewPatterns, PatternSynonyms #-}
+{-# LANGUAGE TemplateHaskell, ForeignFunctionInterface #-}
+{-# LANGUAGE ViewPatterns, PatternSynonyms #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -53,6 +54,8 @@
 import qualified Data.ByteString.Unsafe as B
 import qualified Data.ByteString.Lazy as L
 import qualified Data.ByteString.Lazy.Char8 as C8L
+import           Paths_ngx_export (version)
+import           Data.Version
 
 pattern I l <- (fromIntegral -> l)
 pattern PtrLen s l <- (s, I l)
@@ -73,13 +76,15 @@
                | UnsafeHandler (B.ByteString ->
                                     (B.ByteString, B.ByteString, Int))
 
-let name = mkName "exportType" in sequence
-    [sigD name [t|NgxExport -> IO CInt|],
-     funD name $
-         map (\(c, i) -> clause [conP c [wildP]] (normalB [|return i|]) [])
-             (zip ['SS, 'SSS, 'SLS, 'BS, 'BSS, 'BLS, 'YY, 'BY, 'IOYY, 'IOYYY,
-                   'Handler, 'UnsafeHandler] [1 ..] :: [(Name, Int)])
-    ]
+let name = mkName "exportType" in do
+    TyConI (DataD _ _ _ _ cs _) <- reify ''NgxExport
+    let cons = map (\(NormalC con _) -> con) cs
+    sequence
+        [sigD name [t|NgxExport -> IO CInt|],
+         funD name $
+             map (\(c, i) -> clause [conP c [wildP]] (normalB [|return i|]) [])
+                 (zip cons [1 ..] :: [(Name, Int)])
+        ]
 
 ngxExport' :: (Name -> Q Exp) -> Name -> Name -> Q Type -> Name -> Q [Dec]
 ngxExport' m e h t f = sequence
@@ -179,6 +184,9 @@
 -- | Exports a function of type
 -- /'L.ByteString' -> 'B.ByteString' -> 'IO' 'L.ByteString'/
 -- for using in directive /haskell_run_async_on_request_body/.
+--
+-- The first argument of the exported function contains buffers of the client
+-- request body.
 ngxExportAsyncOnReqBody =
     ngxExport 'IOYYY 'asyncIOYYY
     [t|Ptr NgxStrType -> CInt -> CString -> CInt ->
@@ -433,4 +441,11 @@
     PtrLen smt lmt <- B.unsafeUseAsCStringLen mt return
     pokeCStringLen smt lmt pt plt
     return st
+
+foreign export ccall ngxExportVersion :: Ptr CInt -> IO CInt
+
+ngxExportVersion :: Ptr CInt -> IO CInt
+ngxExportVersion x = fromIntegral <$>
+    foldM (\k (I v) -> pokeElemOff x k v >> return (k + 1)) 0
+        (take 4 $ versionBranch version)
 
diff --git a/ngx-export.cabal b/ngx-export.cabal
--- a/ngx-export.cabal
+++ b/ngx-export.cabal
@@ -1,5 +1,5 @@
 name:                ngx-export
-version:             0.3.0.0
+version:             0.3.1.0
 synopsis:            Helper module for Nginx haskell module
 description:         Helper module for
         <http://github.com/lyokha/nginx-haskell-module Nginx haskell module>
@@ -22,4 +22,5 @@
                      , unix
                      , async >= 2.0
   exposed-modules:     NgxExport
+  other-modules:       Paths_ngx_export