diff --git a/src/Network/MessagePack/Rpc.hs b/src/Network/MessagePack/Rpc.hs
index 3a1df7e..390cbbe 100644
--- a/src/Network/MessagePack/Rpc.hs
+++ b/src/Network/MessagePack/Rpc.hs
@@ -19,6 +19,11 @@ import qualified Network.MessagePack.Interface.Internal as I
 import qualified Network.MessagePack.Types.Client       as Client
 import qualified Network.MessagePack.Types.Server       as Server
 
+-- Import orphan instances for RpcType and IsReturnType.
+-- TODO(SX91): Avoid orphan instances. See issue #7.
+import           Network.MessagePack.Client.Basic       ()
+import           Network.MessagePack.Server.Basic       ()
+
 
 class RpcService rpc where
   type ClientMonad rpc :: * -> *