This simple program module Foo where foo = seq yields the error $ hmake -v -hat Type7.hs hat-trans Type7.hs Creating directories Hat Wrote Hat/Type7.hs /usr/bin/haskell-compiler -v -c -package hat -o Hat/Type7.o Hat/Type7.hs Glasgow Haskell Compiler, Version 6.4, for Haskell 98, compiled by GHC version 6.2.2 Using package config file: /usr/lib/ghc-6.4/package.conf Hsc static flags: -static *** Checking old interface for Hat.Foo: *** Parser: *** Renamer/typechecker: Hat/Type7.hs:12:40: Could not find module `Hat.PreludeBuiltin': locations searched: Hat/PreludeBuiltin.hi Hat/PreludeBuiltin.hi-boot In a lambda abstraction: \ p -> gseq p2v7v2v9 p In the third argument of `Hat.Hat.constDef', namely `(\ p -> gseq p2v7v2v9 p)' In the definition of `sfoo': sfoo = Hat.Hat.constDef Hat.Hat.mkRoot afoo (\ p -> gseq p2v7v2v9 p) *** Deleting temp files Deleting: /tmp/ghc19433.s Warning: deleting non-existent /tmp/ghc19433.s ...with hat 2.0.4 $ strings /usr/lib/ghc-6.4/imports/hat/Hat/PreludeBuiltin.hi | grep aseq aseq --ken