diff --git a/tools/wpcapslip/Makefile b/tools/wpcapslip/Makefile
index 7780d5753..c3ddd7621 100644
--- a/tools/wpcapslip/Makefile
+++ b/tools/wpcapslip/Makefile
@@ -1,7 +1,7 @@
 CONTIKI=../..
 
 CC=gcc
-CFLAGS=-Wall -I$(CONTIKI)/core -I.
+CFLAGS=-Wall -I$(CONTIKI)/os -I.
 
 all: wpcapslip wpcapstdio Connect.class ConnectSocket.class