diff --git a/make/defs.mk b/make/defs.mk
index d35c064a..1f4c4e34 100644
--- a/make/defs.mk
+++ b/make/defs.mk
@@ -227,10 +227,10 @@ SRC_SUFFIX            += $(sort $(suffix $(wildcard $(TOPDIR)/hdr/*)))
 LOCAL_SRC             += Makefile $(wildcard $(addprefix *,$(SRC_SUFFIX)))
 SRC_HEADERED          += $(shell if [ "$(LOCAL_SRC)" ]; then grep -ic "it services" $(LOCAL_SRC) | $(SED) '/:0$$/ d; s/:.*$$//'; fi)
 SRC_UNHEADERED        += $(filter-out $(SRC_HEADERED),$(LOCAL_SRC))
-LOCAL_C               += $(wildcard *.c)
-LOCAL_CPP             += $(wildcard *.cc *.cpp *.C)
-LOCAL_H               += $(wildcard *.h *.H)
-SFILES                += $(wildcard *.S)
+LOCAL_C               ?= $(wildcard *.c)
+LOCAL_CPP             ?= $(wildcard *.cc *.cpp *.C)
+LOCAL_H               ?= $(wildcard *.h *.H)
+SFILES                ?= $(wildcard *.S)
 #PREREQ_H              += $(foreach dir,$(PREREQ_DIR),$(wildcard $(dir)/*.h))
 ALL_H                 += $(LOCAL_H) $(PREREQ_H)
 SRC_ALL_CPP           += $(LOCAL_C) $(LOCAL_CPP) $(LOCAL_H)