diff --git a/Network/Wai/Application/Classic/RevProxy.hs b/Network/Wai/Application/Classic/RevProxy.hs
--- a/Network/Wai/Application/Classic/RevProxy.hs
+++ b/Network/Wai/Application/Classic/RevProxy.hs
@@ -6,7 +6,8 @@
 import Control.Exception (SomeException)
 import Control.Exception.Lifted (catch)
 import Control.Monad.IO.Class (liftIO)
-import qualified Data.ByteString.Char8 as BS
+import qualified Data.ByteString.Char8 as BS hiding (uncons)
+import qualified Data.ByteString as BS (uncons)
 import Data.Conduit
 import Data.Int
 import Data.Maybe
@@ -26,7 +27,7 @@
   , H.secure = isSecure req
   , H.requestHeaders = addForwardedFor req $ requestHeaders req
   , H.path = pathByteString path'
-  , H.queryString = rawQueryString req
+  , H.queryString = dropQuestion $ rawQueryString req
   , H.requestBody = getBody req len
   , H.method = requestMethod req
   , H.proxy = Nothing
@@ -40,6 +41,9 @@
     src = revProxySrc route
     dst = revProxyDst route
     path' = dst </> (path <\> src)
+    dropQuestion q = case BS.uncons q of
+        Just (63, q') -> q' -- '?' is 63
+        _             -> q
 
 getBody :: Request -> Int64 -> H.RequestBody IO
 getBody req len = H.RequestBodySource len (toBodySource req)
diff --git a/wai-app-file-cgi.cabal b/wai-app-file-cgi.cabal
--- a/wai-app-file-cgi.cabal
+++ b/wai-app-file-cgi.cabal
@@ -1,5 +1,5 @@
 Name:                   wai-app-file-cgi
-Version:                0.5.6.1
+Version:                0.5.6.2
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -40,7 +40,7 @@
                       , containers
                       , directory
                       , filepath
-                      , http-conduit
+                      , http-conduit >= 1.2 && < 1.3
                       , http-date
                       , http-types >= 0.6.9
                       , io-choice
@@ -60,7 +60,7 @@
   HS-Source-Dirs:       test
   Build-Depends:        base >= 4 && < 5
                       , bytestring
-                      , http-conduit
+                      , http-conduit >= 1.2 && < 1.3
                       , http-types
                       , lifted-base
                       , HUnit