diff -urN ghc-9.0.2/compiler/GHC/Unit/State.hs ghc-9.0.2-r1/compiler/GHC/Unit/State.hs
--- ghc-9.0.2/compiler/GHC/Unit/State.hs	2021-10-19 05:20:00.000000000 -0600
+++ ghc-9.0.2-r1/compiler/GHC/Unit/State.hs	2022-02-17 01:04:05.117930250 -0700
@@ -194,7 +194,7 @@
 
 instance Outputable ModuleOrigin where
     ppr ModHidden = text "hidden module"
-    ppr (ModUnusable _) = text "unusable module"
+    ppr (ModUnusable reason) = text "unusable module" $$ ppr reason
     ppr (ModOrigin e res rhs f) = sep (punctuate comma (
         (case e of
             Nothing -> []