diff --git a/inline-r/inline-r.cabal b/inline-r/inline-r.cabal
index a669f3d1..a5d2b072 100644
--- a/inline-r/inline-r.cabal
+++ b/inline-r/inline-r.cabal
@@ -78,7 +78,7 @@ library
       Foreign.R.EventLoop
 --      Language.R.Event
   other-modules:
---    Control.Monad.R.Class
+    Control.Monad.R.Class
 --    Control.Monad.R.Internal
 --    Data.Vector.SEXP.Mutable.Internal
     Internal.Error
diff --git a/inline-r/src/Control/Monad/R/Class.hs b/inline-r/src/Control/Monad/R/Class.hs
index 5fed0f99..67803829 100644
--- a/inline-r/src/Control/Monad/R/Class.hs
+++ b/inline-r/src/Control/Monad/R/Class.hs
@@ -2,15 +2,18 @@
 -- Copyright: (C) 2013 Amgen, Inc.
 --
 
+{-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE DefaultSignatures #-}
+{-# OPTIONS_GHC -fplugin-opt=LiquidHaskell:--skip-module=False #-}
 module Control.Monad.R.Class
   ( MonadR(..)
   , Region
-  , acquireSome
   ) where
 
 import Control.Memory.Region
+import qualified Data.Kind
+import Foreign.C -- only needed to help name resolution in LH
 import Foreign.R
 
 import Control.Applicative
@@ -19,6 +22,12 @@ import Control.Monad.Trans (MonadIO(..))
 import Control.Monad.Primitive (PrimMonad, PrimState)
 import Prelude
 
+-- Synonym for LH
+type EqT = (~)
+
+_f :: EqT a b => CString
+_f = undefined
+
 -- | The class of R interaction monads. For safety, in compiled code we normally
 -- use the 'Language.R.Instance.R' monad. For convenience, in a GHCi session, we
 -- normally use the 'IO' monad directly (by means of a 'MonadR' instance for
@@ -29,15 +38,16 @@ class (Applicative m, MonadIO m, MonadCatch m, MonadMask m, PrimMonad m)
   io :: IO a -> m a
   io = liftIO
 
+  {-@ acquire :: EqT s V => a:SEXP s -> m (TSEXP (Region m) (typeOf a)) @-}
   -- | Acquire ownership in the current region of the given object. This means
   -- that the liveness of the object is guaranteed so long as the current region
   -- remains active (the R garbage collector will not attempt to free it).
-  acquire :: s ~ V => SEXP s a -> m (SEXP (Region m) a)
-  default acquire :: (MonadIO m, Region m ~ G) => SEXP s a -> m (SEXP (Region m) a)
-  acquire = liftIO . protect
+  acquire :: s ~ V => SEXP s -> m (SEXP (Region m))
+  default acquire :: (MonadIO m, Region m ~ G) => SEXP s -> m (SEXP (Region m))
+  acquire = defaultAcquire
 
   -- | A reification of an R execution context, i.e. a "session".
-  data ExecContext m :: *
+  data ExecContext m :: Data.Kind.Type
 
   -- | Get the current execution context.
   getExecContext :: m (ExecContext m)
@@ -47,8 +57,10 @@ class (Applicative m, MonadIO m, MonadCatch m, MonadMask m, PrimMonad m)
   -- For internal use only.
   unsafeRunWithExecContext :: m a -> ExecContext m -> IO a
 
-type Region m = PrimState m
+-- For some reason the implementation below causes LH
+-- to fail.
+{-@ ignore defaultAcquire @-}
+defaultAcquire :: MonadIO m => SEXP s -> m (SEXP G)
+defaultAcquire = liftIO . protect
 
--- | 'acquire' for 'SomeSEXP'.
-acquireSome :: (MonadR m) => SomeSEXP V -> m (SomeSEXP (Region m))
-acquireSome (SomeSEXP s) = SomeSEXP <$> acquire s
+type Region m = PrimState m