diff --git a/cardano-api/internal/Cardano/Api/Eras/Core.hs b/cardano-api/internal/Cardano/Api/Eras/Core.hs
index 2dca472604..d9212ceebc 100644
--- a/cardano-api/internal/Cardano/Api/Eras/Core.hs
+++ b/cardano-api/internal/Cardano/Api/Eras/Core.hs
@@ -191,7 +191,8 @@ monoidForEraInEonA sbe = forEraInEon sbe (pure mempty)
 
 data EraInEon eon where
   EraInEon
-    :: ( Typeable (eon era)
+    :: ( Typeable era
+       , Typeable (eon era)
        , Eon eon
        )
     => eon era