diff --git a/compiler/Setup.hs b/compiler/Setup.hs
index c112aaba549..fcbe0b25b1a 100644
--- a/compiler/Setup.hs
+++ b/compiler/Setup.hs
@@ -119,6 +119,8 @@ generateConfigHs :: String -- ^ ghc's cabal-generated unit-id, which matches its
                  -> String -- ^ ghc-internal's cabal-generated unit-id, which matches its package-id/key
                  -> [(String,String)] -> String
 generateConfigHs cProjectUnitId cGhcInternalUnitId settings = either error id $ do
+    -- cStage = 2 is clearly wrong. As we compile the stage 1 compiler with this
+    -- file as well!
     let getSetting' = getSetting $ (("cStage","2"):) settings
     buildPlatform  <- getSetting' "cBuildPlatformString" "Host platform"
     hostPlatform   <- getSetting' "cHostPlatformString" "Target platform"