diff --git a/src/Servant/API/ReqBody.hs b/src/Servant/API/ReqBody.hs
index b601da16..550275aa 100644
--- a/src/Servant/API/ReqBody.hs
+++ b/src/Servant/API/ReqBody.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE PolyKinds #-}
 module Servant.API.ReqBody where
 
 -- | Extract the request body as a value of type @a@.