diff --git a/lib/ip.h b/lib/ip.h
index c3f3e905..cc6be384 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -61,7 +61,7 @@ typedef struct ip4_addr {
 
 typedef u32 ip4_addr;
 
-#define _MI4(x) (x)
+#define _MI4(x) ((u32) (x))
 #define _I(x) (x)
 
 #endif