diff --git a/pkgs/development/libraries/haskell/http-conduit/default.nix b/pkgs/development/libraries/haskell/http-conduit/default.nix
index 5b58909231d3..6621f13df8e9 100644
--- a/pkgs/development/libraries/haskell/http-conduit/default.nix
+++ b/pkgs/development/libraries/haskell/http-conduit/default.nix
@@ -1,19 +1,19 @@
 { cabal, asn1Data, attoparsec, attoparsecConduit, base64Bytestring
 , blazeBuilder, blazeBuilderConduit, caseInsensitive, certificate
 , conduit, cookie, cprngAes, dataDefault, failure, httpTypes
-, liftedBase, monadControl, network, regexCompat, socks, text, time
-, tls, tlsExtra, transformers, transformersBase, utf8String
+, liftedBase, monadControl, mtl, network, regexCompat, socks, text
+, time, tls, tlsExtra, transformers, transformersBase, utf8String
 , zlibConduit
 }:
 
 cabal.mkDerivation (self: {
   pname = "http-conduit";
-  version = "1.2.5";
-  sha256 = "0mb85akb7mgdhjkmp041lhqir2gys9bjixn2v1i848mijw1zx8zr";
+  version = "1.2.6";
+  sha256 = "0gspqkydw5v4wb9s0ipy5s708nmqp3phkh3j95mzn6nlbk2r9kvn";
   buildDepends = [
     asn1Data attoparsec attoparsecConduit base64Bytestring blazeBuilder
     blazeBuilderConduit caseInsensitive certificate conduit cookie
-    cprngAes dataDefault failure httpTypes liftedBase monadControl
+    cprngAes dataDefault failure httpTypes liftedBase monadControl mtl
     network regexCompat socks text time tls tlsExtra transformers
     transformersBase utf8String zlibConduit
   ];