diff --git a/hal/riscv64/generic/types.h b/hal/riscv64/generic/types.h
index 333405fe..04f3517d 100644
--- a/hal/riscv64/generic/types.h
+++ b/hal/riscv64/generic/types.h
@@ -16,7 +16,7 @@
 #ifndef _TYPES_H_
 #define _TYPES_H_
 
-#define NULL 0
+#define NULL ((void *)0)
 
 typedef unsigned char u8;
 typedef unsigned short u16;