diff --git a/cryptol.cabal b/cryptol.cabal
index af43c6169..217b93f35 100644
--- a/cryptol.cabal
+++ b/cryptol.cabal
@@ -177,6 +177,7 @@ library
                        Cryptol.TypeCheck.FFI.FFIType,
                        Cryptol.TypeCheck.Module,
                        Cryptol.TypeCheck.ModuleInstance,
+                       Cryptol.TypeCheck.ModuleBacktickInstance,
 
                        Cryptol.TypeCheck.Solver.Types,
                        Cryptol.TypeCheck.Solver.SMT,
diff --git a/src/Cryptol/ModuleSystem/Base.hs b/src/Cryptol/ModuleSystem/Base.hs
index fa61748eb..035fa6e56 100644
--- a/src/Cryptol/ModuleSystem/Base.hs
+++ b/src/Cryptol/ModuleSystem/Base.hs
@@ -468,7 +468,7 @@ findDeps' m =
                   DefaultInstArg a -> loadInstArg a
                   DefaultInstAnonArg ds -> mconcat (map depsOfDecl ds)
                   NamedInstArgs args -> mconcat (map loadNamedInstArg args)
-                  BacktickInstnace -> mempty
+                  BacktickInstance -> mempty
       in fds <> ads
     InterfaceModule s -> mconcat (map loadImpD (sigImports s))
   where
diff --git a/src/Cryptol/ModuleSystem/Renamer.hs b/src/Cryptol/ModuleSystem/Renamer.hs
index c8274605f..36d7a34ca 100644
--- a/src/Cryptol/ModuleSystem/Renamer.hs
+++ b/src/Cryptol/ModuleSystem/Renamer.hs
@@ -292,7 +292,7 @@ checkFunctorArgs args =
       panic "checkFunctorArgs" ["Nested DefaultInstAnonArg"]
     DefaultInstArg l -> checkArg l
     NamedInstArgs as -> mapM_ checkNamedArg as
-    BacktickInstnace -> pure ()
+    BacktickInstance -> pure ()
   where
   checkNamedArg (ModuleInstanceNamedArg _ l) = checkArg l
 
@@ -481,7 +481,7 @@ renameTopDecls' ds =
                   DefaultInstArg arg -> depsOfArg arg
                   NamedInstArgs args -> concatMap depsOfNamedArg args
                   DefaultInstAnonArg {} -> []
-                  BacktickInstnace -> []
+                  BacktickInstance -> []
 
                where depsOfNamedArg (ModuleInstanceNamedArg _ a) = depsOfArg a
                      depsOfArg a = case thing a of
@@ -795,7 +795,7 @@ instance Rename ModuleInstanceArgs where
       DefaultInstArg a -> DefaultInstArg <$> rnLocated rename a
       NamedInstArgs xs -> NamedInstArgs  <$> traverse rename xs
       DefaultInstAnonArg {} -> panic "rename" ["DefaultInstAnonArg"]
-      BacktickInstnace -> pure BacktickInstnace
+      BacktickInstance -> pure BacktickInstance
 
 instance Rename ModuleInstanceNamedArg where
   rename (ModuleInstanceNamedArg x m) =
diff --git a/src/Cryptol/Parser/AST.hs b/src/Cryptol/Parser/AST.hs
index f2997319a..6c78a019d 100644
--- a/src/Cryptol/Parser/AST.hs
+++ b/src/Cryptol/Parser/AST.hs
@@ -282,9 +282,9 @@ data ModuleInstanceArgs name =
 
   | NamedInstArgs  [ModuleInstanceNamedArg name]
 
-  | BacktickInstnace
+  | BacktickInstance
     -- ^ The module instance is computed by adding the functor arguments
-    -- as explicit parameters to all declarations
+    -- as explicit parameters to all declarations.
     deriving (Show, Generic, NFData)
 
 -- | A named argument in a functor instantiation
@@ -867,7 +867,7 @@ instance (Show name, PPName name) => PP (ModuleInstanceArgs name) where
       DefaultInstArg x -> braces (pp (thing x))
       DefaultInstAnonArg ds -> "where" $$ indent 2 (vcat (map pp ds))
       NamedInstArgs xs -> braces (commaSep (map pp xs))
-      BacktickInstnace -> "{}"
+      BacktickInstance -> "{}"
 
 instance (Show name, PPName name) => PP (ModuleInstanceNamedArg name) where
   ppPrec _ (ModuleInstanceNamedArg x y) = pp (thing x) <+> "=" <+> pp (thing y)
@@ -1363,7 +1363,7 @@ instance NoPos (ModuleInstanceArgs name) where
       DefaultInstArg a      -> DefaultInstArg (noPos a)
       DefaultInstAnonArg ds -> DefaultInstAnonArg (noPos ds)
       NamedInstArgs xs      -> NamedInstArgs (noPos xs)
-      BacktickInstnace      -> BacktickInstnace
+      BacktickInstance      -> BacktickInstance
 
 instance NoPos (ModuleInstanceNamedArg name) where
   noPos (ModuleInstanceNamedArg x y) =
diff --git a/src/Cryptol/TypeCheck/Module.hs b/src/Cryptol/TypeCheck/Module.hs
index 102b1f9f8..d6497ab82 100644
--- a/src/Cryptol/TypeCheck/Module.hs
+++ b/src/Cryptol/TypeCheck/Module.hs
@@ -24,6 +24,7 @@ import Cryptol.TypeCheck.Solve(proveImplication)
 import Cryptol.TypeCheck.Monad
 import Cryptol.TypeCheck.Instantiate(instantiateWith)
 import Cryptol.TypeCheck.ModuleInstance
+import Cryptol.TypeCheck.ModuleBacktickInstance(doBacktickInstance)
 
 doFunctorInst ::
   Located (P.ImpName Name)    {- ^ Name for the new module -} ->
@@ -39,24 +40,25 @@ doFunctorInst m f as inst doc =
   inRange (srcRange m)
   do mf    <- lookupFunctor (thing f)
      argIs <- checkArity (srcRange f) mf as
-     (tySus,decls) <- unzip <$> mapM checkArg argIs
-
-
-     let ?tSu = mergeDistinctSubst tySus
-         ?vSu = inst
-     let m1   = moduleInstance mf
-         m2   = m1 { mName             = m
-                   , mDoc              = Nothing
-                   , mParamTypes       = mempty
-                   , mParamFuns        = mempty
-                   , mParamConstraints = mempty
-                   , mParams           = mempty
-                   -- XXX: Should we modify `mImports` to record dependencies
-                   -- on parameters?
-                   , mDecls = map NonRecursive (concat decls) ++ mDecls m1
-                   }
-
-     newGoals CtModuleInstance (map thing (mParamConstraints m1))
+     m2 <- case argIs of
+             UseArgs ais ->
+               do (tySus,decls) <- unzip <$> mapM checkArg ais
+                  let ?tSu = mergeDistinctSubst tySus
+                      ?vSu = inst
+                  let m1   = moduleInstance mf
+                      m2   = m1 { mName             = m
+                                , mDoc              = Nothing
+                                , mParamTypes       = mempty
+                                , mParamFuns        = mempty
+                                , mParamConstraints = mempty
+                                , mParams           = mempty
+                                , mDecls = map NonRecursive (concat decls) ++
+                                          mDecls m1
+                                }
+                  newGoals CtModuleInstance (map thing (mParamConstraints m1))
+                  pure m2
+
+             AddParamsToDecls -> doBacktickInstance m mf inst
 
      case thing m of
        P.ImpTop mn    -> newModuleScope mn (mExports m2)
@@ -75,6 +77,15 @@ doFunctorInst m f as inst doc =
        P.ImpNested {} -> endSubmodule >> pure Nothing
 
 
+  
+data ActualArg =
+    UseParameter ModParam     -- ^ Instantiate using this parameter
+  | UseModule (IfaceG ())     -- ^ Instantiate using this module
+
+data ActualArgs =
+    UseArgs [(Range, ModParam, ActualArg)]
+  | AddParamsToDecls
+
 
 
 {- | Validate a functor application, just checking the argument names.
@@ -88,7 +99,7 @@ checkArity ::
   Range             {- ^ Location for reporting errors -} ->
   ModuleG ()        {- ^ The functor being instantiated -} ->
   P.ModuleInstanceArgs Name {- ^ The arguments -} ->
-  InferM [ (Range, ModParam, Either ModParam (IfaceG ())) ]
+  InferM ActualArgs
   {- ^ Associates functor parameters with the interfaces of the
        instantiating modules -}
 checkArity r mf args =
@@ -102,8 +113,9 @@ checkArity r mf args =
 
     P.NamedInstArgs as -> checkArgs [] ps0 as
 
-    P.DefaultInstAnonArg {} -> panic "checkArity" [ "DefaultInstAnonArg" ]
+    P.BacktickInstance -> pure AddParamsToDecls
 
+    P.DefaultInstAnonArg {} -> panic "checkArity" [ "DefaultInstAnonArg" ]
   where
   ps0 = mParams mf
 
@@ -112,13 +124,13 @@ checkArity r mf args =
 
       [] -> do forM_ (Map.keys ps) \p ->
                  recordErrorLoc (Just r) (FunctorInstanceMissingArgument p)
-               pure done
+               pure (UseArgs done)
 
       P.ModuleInstanceNamedArg ll lm : more ->
         case Map.lookup (thing ll) ps of
           Just i ->
             do arg <- case thing lm of
-                        P.ModuleArg m -> Just . Right <$> lookupModule m
+                        P.ModuleArg m -> Just . UseModule <$> lookupModule m
                         P.ParameterArg p ->
                            do mb <- lookupModParam p
                               case mb of
@@ -126,7 +138,7 @@ checkArity r mf args =
                                    do inRange (srcRange lm)
                                               (recordError (MissingModParam p))
                                       pure Nothing
-                                Just a -> pure (Just (Left a))
+                                Just a -> pure (Just (UseParameter a))
                let next = case arg of
                             Nothing -> done
                             Just a  -> (srcRange lm, i, a) : done
@@ -148,7 +160,7 @@ Returns:
     values.
 -}
 checkArg ::
-  (Range, ModParam, Either ModParam (IfaceG ())) -> InferM (Subst, [Decl])
+  (Range, ModParam, ActualArg) -> InferM (Subst, [Decl])
 checkArg (r,expect,actual') =
   do tRens <- mapM (checkParamType r tyMap) (Map.toList (mpnTypes params))
      let renSu = listParamSubst (concat tRens)
@@ -175,15 +187,16 @@ checkArg (r,expect,actual') =
   vMap  :: Map Ident (Name, Schema)
   (tyMap,vMap) =
     case actual' of
-      Left mp -> ( nameMapToIdentMap fromTP (mpnTypes ps)
-                 , nameMapToIdentMap fromVP (mpnFuns ps)
-                 )
+      UseParameter mp ->
+        ( nameMapToIdentMap fromTP (mpnTypes ps)
+        , nameMapToIdentMap fromVP (mpnFuns ps)
+        )
         where
         ps        = mpParameters mp
         fromTP tp = (mtpKind tp, TVar (TVBound (mtpParam tp)))
         fromVP vp = (mvpName vp, mvpType vp)
 
-      Right actual ->
+      UseModule actual ->
         ( Map.unions [ nameMapToIdentMap fromTS      (ifTySyns decls)
                      , nameMapToIdentMap fromNewtype (ifNewtypes decls)
                      , nameMapToIdentMap fromPrimT   (ifAbstractTypes decls)
diff --git a/src/Cryptol/TypeCheck/ModuleBacktickInstance.hs b/src/Cryptol/TypeCheck/ModuleBacktickInstance.hs
new file mode 100644
index 000000000..463480245
--- /dev/null
+++ b/src/Cryptol/TypeCheck/ModuleBacktickInstance.hs
@@ -0,0 +1,16 @@
+module Cryptol.TypeCheck.ModuleBacktickInstance where
+
+import Data.Map(Map)
+import qualified Data.Map as Map
+
+import Cryptol.Parser.Position (Located(..), thing)
+import qualified Cryptol.Parser.AST as P
+import Cryptol.TypeCheck.AST
+import Cryptol.TypeCheck.Monad
+
+doBacktickInstance ::
+  Located (P.ImpName Name)    {- ^ Name for the new module -} ->
+  ModuleG ()                  {- ^ The functor -} ->
+  Map Name Name {- ^ The instantiation: functor name -> instance name -} ->
+  InferM (ModuleG (Located (P.ImpName Name)))
+doBacktickInstance m mf inst = undefined