diff --git a/Makefile b/Makefile
index 1496c7f..4d85a03 100644
--- a/Makefile
+++ b/Makefile
@@ -21,6 +21,7 @@ CFLAGS += -ffreestanding
 CFLAGS += -fno-common
 CFLAGS += -nostdlib
 CFLAGS += -mno-relax
+CFLAGS += -std=gnu99
 
 CFLAGS += -fno-stack-protector # Prevents code that needs libc / runtime support
 CFLAGS += -MD # Generate header dependency files (.d)