diff --git a/servers/slapd/syncrepl.c b/servers/slapd/syncrepl.c
index aadf33b79c..eada1d56db 100644
--- a/servers/slapd/syncrepl.c
+++ b/servers/slapd/syncrepl.c
@@ -1353,6 +1353,8 @@ do_syncrepl(
 
 	connection_fake_init( &conn, &opbuf, ctx );
 	op = &opbuf.ob_op;
+	/* o_connids must be unique for slap_graduate_commit_csn */
+	op->o_connid = -1000 - si->si_rid;
 
 	op->o_managedsait = SLAP_CONTROL_NONCRITICAL;
 	be = si->si_be;