GHC_OPTS += $(addprefix -optc, $(MACOSX_DEPLOYMENT_CC_OPTS))
LIB_LD_OPTS += $(addprefix -optl, $(MACOSX_DEPLOYMENT_LD_OPTS))
+# Work around a bug "splitTyConApp e1{tv a2iZ}" in 6.4.2:
+ifeq "$(ghc_ge_605)" "NO"
+dist-stage1/build/IOEnv.o: GHC_OPTS += -O0
+endif
+
# XXX These didn't work in the old build system, according to the
# comment at least. We should actually handle them properly at some
# point: