diff --git a/src/Compiler/RLPC.hs b/src/Compiler/RLPC.hs
index 518e9fb..5acedc6 100644
--- a/src/Compiler/RLPC.hs
+++ b/src/Compiler/RLPC.hs
@@ -16,6 +16,7 @@ module Compiler.RLPC
     , RLPCT(..)
     , RLPCIO
     , RLPCOptions(RLPCOptions)
+    , IsRlpcError(..)
     , RlpcError(..)
     , addFatal
     , addWound
@@ -56,8 +57,7 @@ import Lens.Micro.TH
 ----------------------------------------------------------------------------------
 
 newtype RLPCT m a = RLPCT {
-        runRLPCT :: forall e. (RlpcError e)
-                 => ReaderT RLPCOptions (ErrorfulT e m) a
+        runRLPCT :: ReaderT RLPCOptions (ErrorfulT RlpcError m) a
     }
 
 type RLPC = RLPCT Identity
@@ -72,7 +72,7 @@ evalRLPC = undefined
 evalRLPCT = undefined
 evalRLPCIO = undefined
 
-liftErrorful :: (RlpcError e) => ErrorfulT e m a -> RLPCT m a
+liftErrorful :: ErrorfulT e m a -> RLPCT m a
 liftErrorful e = undefined
 
 data RLPCOptions = RLPCOptions
diff --git a/src/Compiler/RlpcError.hs b/src/Compiler/RlpcError.hs
index cd53964..755f05d 100644
--- a/src/Compiler/RlpcError.hs
+++ b/src/Compiler/RlpcError.hs
@@ -1,9 +1,9 @@
 {-# LANGUAGE TemplateHaskell #-}
 module Compiler.RlpcError
-    ( RlpcError(..)
+    ( IsRlpcError(..)
     , MsgEnvelope(..)
     , Severity
-    , RlpcErrorDoc(..)
+    , RlpcError(..)
     , SrcSpan(..)
     , msgSpan
     , msgDiagnostic
@@ -15,16 +15,16 @@ import Control.Monad.Errorful
 import Lens.Micro.TH
 ----------------------------------------------------------------------------------
 
-data MsgEnvelope = MsgEnvelope
+data MsgEnvelope e = MsgEnvelope
    { _msgSpan        :: SrcSpan
-   , _msgDiagnostic  :: forall e. (RlpcError e) => e
+   , _msgDiagnostic  :: e
    , _msgSeverity    :: Severity
    }
 
-class RlpcError e where
-    liftRlpcError :: e -> RlpcErrorDoc
+class IsRlpcError e where
+    liftRlpcError :: e -> RlpcError
 
-data RlpcErrorDoc
+data RlpcError
 
 data Severity = SevWarning
               | SevError
diff --git a/src/Core/HindleyMilner.hs b/src/Core/HindleyMilner.hs
index ed01359..12c7436 100644
--- a/src/Core/HindleyMilner.hs
+++ b/src/Core/HindleyMilner.hs
@@ -49,7 +49,7 @@ data TypeError
     deriving (Show, Eq)
 
 -- TODO:
-instance RlpcError TypeError where
+instance IsRlpcError TypeError where
 
 -- | Synonym for @Errorful [TypeError]@. This means an @HMError@ action may
 -- throw any number of fatal or nonfatal errors. Run with @runErrorful@.
diff --git a/src/Core/Lex.x b/src/Core/Lex.x
index d076206..1136409 100644
--- a/src/Core/Lex.x
+++ b/src/Core/Lex.x
@@ -199,10 +199,10 @@ data ParseError = ParErrLexical String
                 deriving Show
 
 -- TODO:
-instance RlpcError SrcError where
+instance IsRlpcError SrcError where
 
 -- TODO:
-instance RlpcError ParseError where
+instance IsRlpcError ParseError where
 
 alexEOF :: Alex (Located CoreToken)
 alexEOF = Alex $ \ st@(AlexState { alex_pos = AlexPn _ y x }) ->