diff --git a/compiler/GHC/IfaceToCore.hs b/compiler/GHC/IfaceToCore.hs
index 60cca252e0a98f30d57c7d501263b48c3cd7cdb2..5d68e0479234ad81decf74644b0aae1d48f6e91b 100644
--- a/compiler/GHC/IfaceToCore.hs
+++ b/compiler/GHC/IfaceToCore.hs
@@ -957,7 +957,7 @@ tc_iface_decl_fingerprint :: Bool                    -- Don't load pragmas into
 tc_iface_decl_fingerprint ignore_prags (_version, decl)
   = do  {       -- Populate the name cache with final versions of all
                 -- the names associated with the decl
-          let main_name = ifName decl
+          let !main_name = ifName decl
 
         -- Typecheck the thing, lazily
         -- NB. Firstly, the laziness is there in case we never need the