diff --git a/ghc/compiler/typecheck/TcEnv.lhs b/ghc/compiler/typecheck/TcEnv.lhs
index 30999e89c20696274266f7c07adf17e83254621f..c99244d20496f343590c1e4db1fab79ede3530db 100644
--- a/ghc/compiler/typecheck/TcEnv.lhs
+++ b/ghc/compiler/typecheck/TcEnv.lhs
@@ -72,6 +72,7 @@ import Unique		( pprUnique10, Unique, Uniquable(..) )
 import UniqFM
 import Unique		( Uniquable(..) )
 import Util		( zipEqual, zipWith3Equal, mapAccumL )
+import VarEnv		( TyVarSubstEnv )
 import SrcLoc		( SrcLoc )
 import FastString	( FastString )
 import Maybes