diff --git a/servers/slapd/syncrepl.c b/servers/slapd/syncrepl.c
index a921453294..30f4c63dc5 100644
--- a/servers/slapd/syncrepl.c
+++ b/servers/slapd/syncrepl.c
@@ -1214,8 +1214,9 @@ do_syncrepl(
 	if ( si == NULL )
 		return NULL;
 
-	/* There will never be more than one instance active */
-	ldap_pvt_thread_mutex_lock( &si->si_mutex );
+	/* There must never be more than one instance active */
+	if ( ldap_pvt_thread_mutex_trylock( &si->si_mutex ))
+		return NULL;
 
 	switch( abs( si->si_type ) ) {
 	case LDAP_SYNC_REFRESH_ONLY: