-DERIVED_SRCS = $(patsubst %.hsc, %.hs %_hsc.c %_hsc.h, \
- $(filter %.hsc, $(PRE_SRCS) ))
+HSC_SRCS = $(filter %.hsc, $(PRE_SRCS))
+DERIVED_SRCS = $(patsubst %.hsc, %.hs, $(HSC_SRCS)) \
+ $(patsubst %.hsc, %_hsc.c, $(HSC_SRCS)) \
+ $(patsubst %.hsc, %_hsc.h, $(HSC_SRCS))