Index: modules/metadata/mod_expires.c
===================================================================
--- modules/metadata/mod_expires.c	(revision 685653)
+++ modules/metadata/mod_expires.c	(working copy)
@@ -397,6 +397,7 @@
     apr_time_t base;
     apr_time_t additional;
     apr_time_t expires;
+    apr_time_t e;
     int additional_sec;
     char *timestr;
 
@@ -428,11 +429,15 @@
                     "internal error: bad expires code: %s", r->filename);
         return HTTP_INTERNAL_SERVER_ERROR;
     }
-
+    /* Do not let max-age be negetive.
+     */
+    e = apr_time_sec(base - r->request_time) + apr_time_sec(additional);
+    if (e < 0) e = APR_INT64_MAX;
     expires = base + additional;
+    if (expires < 0) expires = APR_INT64_MAX;
     apr_table_mergen(t, "Cache-Control",
                      apr_psprintf(r->pool, "max-age=%" APR_TIME_T_FMT,
-                                  apr_time_sec(expires - r->request_time)));
+                                  e));
     timestr = apr_palloc(r->pool, APR_RFC822_DATE_LEN);
     apr_rfc822_date(timestr, expires);
     apr_table_setn(t, "Expires", timestr);