diff --git a/compiler/stranal/WwLib.lhs b/compiler/stranal/WwLib.lhs
index 11f97eab078bb641bcca288825914a44037660f8..1f1fbdf745fcde2938ebdae0869d6f3c9104a8f0 100644
--- a/compiler/stranal/WwLib.lhs
+++ b/compiler/stranal/WwLib.lhs
@@ -528,7 +528,8 @@ can still be specialised by the type-class specialiser, something like
 
 BUT if f is strict in the Ord dictionary, we might unpack it, to get
    fw :: (a->a->Bool) -> [a] -> Int# -> a
-and the type-class specialiser can't specialise that.
+and the type-class specialiser can't specialise that.  An example is
+Trac #6056.
 
 Moreover, dictinoaries can have a lot of fields, so unpacking them can
 increase closure sizes.