diff --git a/simple-sendfile.cabal b/simple-sendfile.cabal
--- a/simple-sendfile.cabal
+++ b/simple-sendfile.cabal
@@ -1,5 +1,5 @@
 Name:                   simple-sendfile
-Version:                0.2.14
+Version:                0.2.15
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -46,7 +46,7 @@
         Other-Modules:  Network.Sendfile.Fallback
         Build-Depends:  conduit         >= 1.0 && < 1.2
                       , conduit-extra   >= 1.0 && < 1.2
-                      , transformers    >= 0.2.2 && < 0.4
+                      , transformers    >= 0.2.2 && < 0.5
 
 Test-Suite spec
   Type:                 exitcode-stdio-1.0