diff --git a/package/network/ipv6/6rd/Makefile b/package/network/ipv6/6rd/Makefile
index 3ab8198ef3..d4b65afb23 100644
--- a/package/network/ipv6/6rd/Makefile
+++ b/package/network/ipv6/6rd/Makefile
@@ -35,6 +35,7 @@ define Build/Compile
 	$(MAKE) -C $(PKG_BUILD_DIR) \
 		CC="$(TARGET_CC)" \
 		CFLAGS="$(TARGET_CFLAGS) -Wall" \
+		CPPFLAGS="$(TARGET_CPPFLAGS)" \
 		LDFLAGS="$(TARGET_LDFLAGS)"
 endef
 
diff --git a/package/network/ipv6/6rd/src/Makefile b/package/network/ipv6/6rd/src/Makefile
index 2881d43589..526ffcaeb0 100644
--- a/package/network/ipv6/6rd/src/Makefile
+++ b/package/network/ipv6/6rd/src/Makefile
@@ -1,7 +1,7 @@
 all: 6rdcalc
 
 6rdcalc: 6rdcalc.c
-	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -o $@ $<
 
 clean:
 	rm -f 6rdcalc