diff --git a/ntp_sources.c b/ntp_sources.c
index 64d9a8b..29c99ac 100644
--- a/ntp_sources.c
+++ b/ntp_sources.c
@@ -770,8 +770,19 @@ static int get_unused_pool_id(void)
 static uint32_t
 get_next_conf_id(uint32_t *conf_id)
 {
+  SourceRecord *record;
+  unsigned int i;
+
+again:
   last_conf_id++;
 
+  /* Make sure the ID is not already used (after 32-bit wraparound) */
+  for (i = 0; i < ARR_GetSize(records); i++) {
+    record = get_record(i);
+    if (record->remote_addr && record->conf_id == last_conf_id)
+      goto again;
+  }
+
   if (conf_id)
     *conf_id = last_conf_id;