diff --git a/evaluation/demonstration/Makefile b/evaluation/demonstration/Makefile
index 2e275b26821cc2d3dbe4a5287e0d113b613e7ce0..a90f47e987ff84f912a408a8086229c3dec69684 100644
--- a/evaluation/demonstration/Makefile
+++ b/evaluation/demonstration/Makefile
@@ -1,4 +1,4 @@
-CFLAGS=-g -I../../include
+CFLAGS=-g -std=gnu11 -I../../include
 LIBS=-lssl -lcrypto -lpthread -ldl
 LDFLAGS=-L../..
 TARGETS=client server middlebox