diff --git a/Makefile b/Makefile
index 6f9775b..6fe9144 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 CRYPTO_CFLAGS := $(shell pkg-config --cflags libcrypto)
 CRYPTO_LDLIBS := $(shell pkg-config --libs libcrypto)
 
-CFLAGS += -Wall -Wextra $(CRYPTO_CFLAGS)
+CFLAGS += -std=gnu99 -Wall -Wextra $(CRYPTO_CFLAGS)
 LDLIBS += $(CRYPTO_LDLIBS)
 
 all : torrenthash