diff --git a/server/incoming_spa.c b/server/incoming_spa.c
index ad6268ae..f80a76ea 100644
--- a/server/incoming_spa.c
+++ b/server/incoming_spa.c
@@ -531,8 +531,10 @@ incoming_spa(fko_srv_options_t *opts)
 
         /* Add this SPA packet into the replay detection cache
         */
-        if (added_replay_digest == 0)
+        if (added_replay_digest == 0
+                && strncasecmp(opts->config[CONF_ENABLE_DIGEST_PERSISTENCE], "Y", 1) == 0)
         {
+
             res = add_replay(opts, raw_digest);
             if (res != SPA_MSG_SUCCESS)
             {
diff --git a/server/replay_cache.c b/server/replay_cache.c
index 51e73d3b..3b93f621 100644
--- a/server/replay_cache.c
+++ b/server/replay_cache.c
@@ -730,6 +730,12 @@ add_replay(fko_srv_options_t *opts, char *digest)
     return(-1);
 #else
 
+    if(digest == NULL)
+    {
+        log_msg(LOG_WARNING, "NULL digest passed into add_replay()");
+        return(SPA_MSG_DIGEST_CACHE_ERROR);
+    }
+
 #if USE_FILE_CACHE
     return add_replay_file_cache(opts, digest);
 #else