diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index a698ece43fff..4852bf44e913 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -9,7 +9,7 @@ dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \
 dtc-objs	+= dtc-lexer.lex.o dtc-parser.tab.o
 
 # Source files need to get at the userspace version of libfdt_env.h to compile
-HOST_EXTRACFLAGS := -I $(srctree)/$(src)/libfdt
+HOST_EXTRACFLAGS += -I $(srctree)/$(src)/libfdt
 
 ifeq ($(shell pkg-config --exists yaml-0.1 2>/dev/null && echo yes),)
 ifneq ($(CHECK_DT_BINDING)$(CHECK_DTBS),)