Hello, I have been changing my default ghc around lately on the machinery that I use for Yhc buildbotting. The original was ghc-6.4.1, but with a recent ghc-HEAD, I get errors like these: http://www.indiegigs.co.uk:8010/macosx_ppc_3/builds/15/step-yhc/0 ... scons: Building targets ... Getting dependencies for src/libraries/core/Yhc/Core/Simplify.hs. "ghc" -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c src/libraries/core/Yhc/Core/Simplify.hs -o src/libraries/core/Yhc/Core/Simplify.o src/libraries/core/Yhc/Core/Simplify.hs:7:0: Bad interface file: ./src/libraries/core/Yhc/Core/Type.hi mismatched interface file versions: expected 590528065, found 6 scons: *** [src/libraries/core/Yhc/Core/Simplify.o] Error 1 scons: building terminated because of errors. program finished with exit code 2 I presume that this is because the buildbot-controlled build is incremental so that when I change the ghc version used, inconsistencies result. So the question is this: When I change my ghc version, how do I clean up the Yhc buildbot build tree to ensure that everything gets built with the new ghc version? Thanks and best regards Thorkil