diff --git a/make/defs.mk b/make/defs.mk
index 4ae14fda..27dcfdd1 100644
--- a/make/defs.mk
+++ b/make/defs.mk
@@ -224,13 +224,13 @@ INSTALLED_SYSCFG      ?= $(addprefix $(INSTALL_SYSCFGDIR)/,$(SYSCFG_FILES))
 
 # -- HDR
 # why both SRC_H <-> LOCAL_H?
-BUILD_HDRDIR           = $(TOPDIR)/include
+BUILD_HDRDIR          ?= $(TOPDIR)/include
 LOCAL_H               += $(wildcard *.h *.H)
 SRC_H                 += $(filter %.h %.H, $(SRC_ALL_CPP))
-BUILD_H               += $(patsubst %.h,$(TOPDIR)/include/%.h,$(SRC_H))
+BUILD_H                = $(addprefix $(BUILD_HDRDIR)/,$(SRC_H))
+BUILD_HDR              = $(addprefix $(BUILD_HDRDIR)/,$(SRC_H))
 PREREQ_H              += $(foreach dir,$(PREREQ_DIR),$(wildcard $(dir)/*.h))  
 ALL_H                 += $(LOCAL_H) $(PREREQ_H)
-BUILD_HDR              = $(addprefix $(BUILD_HDRDIR)/,$(SRC_H))
 INSTALL_HDRDIR        ?= $(PREFIX)/include
 INSTALLED_HDR         += $(addprefix $(INSTALL_HDRDIR)/,$(SRC_H))