diff --git a/Makefile b/Makefile
index 6b41f99..84e563d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 all: test
 
 test: test.c uprintf.c uprintf.h
-	gcc -Os -m32 -o test test.c uprintf.c
+	gcc -std=c99 -Os -m32 -o test test.c uprintf.c
 
 clean:
 	rm -rf test