diff --git a/Makefile b/Makefile
index 910f471..da0cfda 100644
--- a/Makefile
+++ b/Makefile
@@ -246,7 +246,7 @@
 
 CFLAGS = -g -O2 -Wall
 LDFLAGS =
-ALL_CFLAGS = $(CFLAGS)
+ALL_CFLAGS = $(CPPFLAGS) $(CFLAGS)
 ALL_LDFLAGS = $(LDFLAGS)
 STRIP ?= strip