diff --git a/Makefile b/Makefile
index 846874e..4b9e702 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-CFLAGS=-Wall -Wextra -pedantic -g -DNDEBUG
+CFLAGS += -Wall -Wextra -pedantic -std=gnu99 -g -DNDEBUG
 
 EXERCISES = $(patsubst %.c,%,$(shell ls ex*.c | egrep -v "ex(19|22)"))