diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,8 @@
+## 5.1.3
+
+* Defining SendRequest type synonym.
+  [#111](https://github.com/kazu-yamamoto/http2/pull/111)
+
 ## 5.1.2
 
 * Make ping rate limit configurable
diff --git a/Network/HTTP2/Client.hs b/Network/HTTP2/Client.hs
--- a/Network/HTTP2/Client.hs
+++ b/Network/HTTP2/Client.hs
@@ -75,6 +75,7 @@
 
     -- * HTTP\/2 client
     Client,
+    SendRequest,
 
     -- * Request
     Request,
diff --git a/Network/HTTP2/Client/Types.hs b/Network/HTTP2/Client/Types.hs
--- a/Network/HTTP2/Client/Types.hs
+++ b/Network/HTTP2/Client/Types.hs
@@ -6,8 +6,11 @@
 
 ----------------------------------------------------------------
 
+-- | Send a request and receive its response.
+type SendRequest = forall r. Request -> (Response -> IO r) -> IO r
+
 -- | Client type.
-type Client a = (forall b. Request -> (Response -> IO b) -> IO b) -> Aux -> IO a
+type Client a = SendRequest -> Aux -> IO a
 
 -- | Request from client.
 newtype Request = Request OutObj deriving (Show)
diff --git a/http2.cabal b/http2.cabal
--- a/http2.cabal
+++ b/http2.cabal
@@ -1,6 +1,6 @@
 cabal-version:      >=1.10
 name:               http2
-version:            5.1.2
+version:            5.1.3
 license:            BSD3
 license-file:       LICENSE
 maintainer:         Kazu Yamamoto <kazu@iij.ad.jp>
@@ -117,12 +117,12 @@
         base >=4.9 && <5,
         array >= 0.5 && < 0.6,
         async >= 2.2 && < 2.3,
-        bytestring >= 0.10 && < 0.13,
+        bytestring >= 0.10,
         containers >= 0.6 && < 0.7,
         stm >= 2.5 && < 2.6,
         case-insensitive >= 1.2 && < 1.3,
         http-types >= 0.12 && < 0.13,
-        network >= 3.1 && < 3.2,
+        network >= 3.1,
         network-byte-order >= 0.1.7 && < 0.2,
         network-control >= 0.0.2 && < 0.1,
         unix-time >= 0.4.11 && < 0.5,