--- crypto/heimdal/lib/krb5/addr_families.c
+++ crypto/heimdal/lib/krb5/addr_families.c
@@ -32,6 +32,7 @@
  */
 

+#include <myloop_masklen.h>
 #include "krb5_locl.h"
 
 struct addr_operations {
     int af;
@@ -142,7 +143,7 @@
 {
     const struct sockaddr_in *sin4 = (const struct sockaddr_in *)sa;
 
-    if ((ntohl(sin4->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET)
+    if (IN_MY_LOOP(ntohl(sin4->sin_addr.s_addr)))
 	return TRUE;
 
     return FALSE;
--- crypto/heimdal/lib/ipc/myloop_masklen.h
+++ crypto/heimdal/lib/ipc/myloop_masklen.h
@@ -0,0 +1,7 @@
+#define	MYLOOP_MASKLEN 24
+
+#ifndef MYLOOP_MASKLEN
+#define	IN_MY_LOOP(i)		(((in_addr_t)(i) & IN_CLASSA_NET) == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
+#else
+#define	IN_MY_LOOP(i)		(((in_addr_t)(i) & (INADDR_BROADCAST << (32 - MYLOOP_MASKLEN))) == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
+#endif