Index: modules/session/mod_session.c
===================================================================
--- modules/session/mod_session.c	(revision 1788360)
+++ modules/session/mod_session.c	(working copy)
@@ -353,11 +353,15 @@
 
     char *buffer = NULL;
     int length = 0;
-    if (z->expiry) {
+
+    apr_table_do(identity_count, &length, z->entries, NULL);
+
+    /* Do not send cookie with just expiry set without any data */
+    if (length > 0 && z->expiry) {
         char *expiry = apr_psprintf(z->pool, "%" APR_INT64_T_FMT, z->expiry);
         apr_table_setn(z->entries, SESSION_EXPIRY, expiry);
     }
-    apr_table_do(identity_count, &length, z->entries, NULL);
+
     buffer = apr_pcalloc(r->pool, length + 1);
     apr_table_do(identity_concat, buffer, z->entries, NULL);
     z->encoded = buffer;