diff --git a/ghc/compiler/usageSP/UsageSPInf.lhs b/ghc/compiler/usageSP/UsageSPInf.lhs
index a95178de8bf5ebc62697c4156a5a15b7cb65a0ee..7fe753e59b39caa02cc8f870e221c3e4e39b524b 100644
--- a/ghc/compiler/usageSP/UsageSPInf.lhs
+++ b/ghc/compiler/usageSP/UsageSPInf.lhs
@@ -423,7 +423,7 @@ usgClos :: VarEnv Var        -- environment to close with respect to
         -> (Type,            -- closed type (rho)
             UConSet)         -- residual constraint set
 
-usgClos _ve ty ucs = (ty,ucs)  -- dummy definition; no generalisation at all
+usgClos zz_ve ty ucs = (ty,ucs)  -- dummy definition; no generalisation at all
 
             -- hmm!  what if it sets some uvars to 1 or omega?
             --  (should it do substitution here, or return a substitution,