diff --git a/makefile b/makefile
index 0fb1afb..aae8666 100644
--- a/makefile
+++ b/makefile
@@ -1,7 +1,7 @@
 TARGET = es_tests
 LIBS = -lm -lcunit -luuid -lprotobuf-c
 CC = gcc
-CFLAGS = -g -std=c99 -Wall
+CFLAGS = -g -std=gnu99 -Wall
 
 .PHONY: all clean test default valgrind