diff --git a/include/ruby/win32.h b/include/ruby/win32.h
index eaa825fd8c..2bdcbc5318 100644
--- a/include/ruby/win32.h
+++ b/include/ruby/win32.h
@@ -273,7 +273,7 @@ extern int    rb_w32_urename(const char *, const char *);
 extern char **rb_w32_get_environ(void);
 extern void   rb_w32_free_environ(char **);
 extern int    rb_w32_map_errno(DWORD);
-extern char * WSAAPI rb_w32_inet_ntop(int,void *,char *,size_t);
+extern char * WSAAPI rb_w32_inet_ntop(int,const void *,char *,size_t);
 extern DWORD  rb_w32_osver(void);
 
 extern int chown(const char *, int, int);
diff --git a/win32/win32.c b/win32/win32.c
index 966688286e..3ab696d59b 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -6130,17 +6130,18 @@ signbit(double x)
 
 /* License: Ruby's */
 char * WSAAPI
-rb_w32_inet_ntop(int af, void *addr, char *numaddr, size_t numaddr_len)
+rb_w32_inet_ntop(int af, const void *addr, char *numaddr, size_t numaddr_len)
 {
     typedef char *(WSAAPI inet_ntop_t)(int, void *, char *, size_t);
     inet_ntop_t *pInetNtop;
     pInetNtop = (inet_ntop_t *)get_proc_address("ws2_32", "inet_ntop", NULL);
-    if(pInetNtop){
-       return pInetNtop(af,addr,numaddr,numaddr_len);
-    }else{
-       struct in_addr in;
-       memcpy(&in.s_addr, addr, sizeof(in.s_addr));
-       snprintf(numaddr, numaddr_len, "%s", inet_ntoa(in));
+    if (pInetNtop) {
+	return pInetNtop(af, (void *)addr, numaddr, numaddr_len);
+    }
+    else {
+	struct in_addr in;
+	memcpy(&in.s_addr, addr, sizeof(in.s_addr));
+	snprintf(numaddr, numaddr_len, "%s", inet_ntoa(in));
     }
     return numaddr;
 }