diff --git a/os/access.c b/os/access.c
index 28f2d32..fe6e831 100644
--- a/os/access.c
+++ b/os/access.c
@@ -1390,14 +1390,23 @@ InvalidHost(register struct sockaddr *saddr, int len, ClientPtr client)
         else
             return 0;
     }
+
+    /* An empty address requires both a NULL addr *and* a zero length
+     * as the address comparison functions call memcmp with both
+     * parameters. Make sure they agree here
+     */
+    if (addr == NULL)
+        len = 0;
+    if (len == 0)
+        addr = NULL;
     for (host = validhosts; host; host = host->next) {
         if (host->family == FamilyServerInterpreted) {
-            if (addr && siAddrMatch(family, addr, len, host, client)) {
+            if (siAddrMatch(family, addr, len, host, client)) {
                 return 0;
             }
         }
         else {
-            if (addr && addrEqual(family, addr, len, host))
+            if (addrEqual(family, addr, len, host))
                 return 0;
         }