diff --git a/Makefile b/Makefile
index 6950051..e765cfe 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
-CC     = c99
-CFLAGS = -O2
+CC     = gcc
+CFLAGS = -O2 -std=c99
 
 all:kseq.h fastool.c
 	$(CC) $(CFLAGS) fastool.c -o fastool -lz