diff --git a/servers/slapd/overlays/syncprov.c b/servers/slapd/overlays/syncprov.c
index 8fb306241b..2cbc9722cc 100644
--- a/servers/slapd/overlays/syncprov.c
+++ b/servers/slapd/overlays/syncprov.c
@@ -783,7 +783,8 @@ syncprov_free_syncop( syncops *so )
 	GroupAssertion *ga, *gnext;
 
 	ldap_pvt_thread_mutex_lock( &so->s_mutex );
-	if ( --so->s_inuse > 0 ) {
+	/* already being freed, or still in use */
+	if ( !so->s_inuse || --so->s_inuse > 0 ) {
 		ldap_pvt_thread_mutex_unlock( &so->s_mutex );
 		return;
 	}