diff --git a/include/net.h b/include/net.h
index 5e3495bd7..95ef8ab83 100644
--- a/include/net.h
+++ b/include/net.h
@@ -514,7 +514,7 @@ static inline int is_valid_ether_addr(const u8 *addr)
 extern void	ip_to_string (IPaddr_t x, char *s);
 
 /* Convert a string to ip address */
-extern IPaddr_t string_to_ip(char *s);
+extern IPaddr_t string_to_ip(const char *s);
 
 /* Convert a VLAN id to a string */
 extern void	VLAN_to_string (ushort x, char *s);
diff --git a/lib/net_utils.c b/lib/net_utils.c
index f03b098e9..b425a68d9 100644
--- a/lib/net_utils.c
+++ b/lib/net_utils.c
@@ -28,7 +28,7 @@
 
 #include <common.h>
 
-IPaddr_t string_to_ip(char *s)
+IPaddr_t string_to_ip(const char *s)
 {
 	IPaddr_t addr;
 	char *e;