diff --git a/Makefile b/Makefile
index 4f5316c..077b8bf 100644
--- a/Makefile
+++ b/Makefile
@@ -67,6 +67,7 @@ STATIC_OBJS= \
 DYNAMIC_OBJS= \
 	$(STATIC_OBJS)
 CFLAGS ?= -g
+CFLAGS += $(CPPFLAGS)
 CFLAGS += -Wall -Werror -Wstrict-prototypes -Wmissing-prototypes
 CFLAGS += -fPIC $(ALERTING) $(LIBPRI_OPT) $(COVERAGE_CFLAGS)
 INSTALL_PREFIX=$(DESTDIR)