diff --git a/CHANGES b/CHANGES
index 8ec6ea2a47ed24b5e4720ebf436936f93efcda36..5ed9a8f2e32196ab9d325ab77ee83e9f436835e8 100644
--- a/CHANGES
+++ b/CHANGES
@@ -14,8 +14,10 @@ OpenLDAP 2.4.22 Engineering
 	Fixed slapd syncrepl for unknown attrs and delta-sync (ITS#6473)
 	Fixed slapd-bdb contextCSN updates from updatedn (ITS#6469)
 	Fixed slapo-collect REP_ENTRY flag handling (ITS#5340,ITS#6423)
+	Fixed slapo-dds with NULL backend (ITS#6490)
 	Fixed slapo-dynlist REP_ENTRY flag handling (ITS#5340,ITS#6423)
 	Fixed slapo-pcache to release its own entries (ITS#6484)
+	Fixed slapo-pcache with NULL backend (ITS#6490)
 	Fixed slapo-rwm entry release handling (ITS#6484)
 	Fixed slapo-rwm olcRwmMap handling (ITS#6436)
 	Fixed slapo-rwm REP_ENTRY flag handling (ITS#5340,ITS#6423)
diff --git a/servers/slapd/overlays/dds.c b/servers/slapd/overlays/dds.c
index 6b579b9b07df17db40068f4eb729c15d6fcc8ac7..c0bbc40d84bff915d79dac946507b59d73c2bc12 100644
--- a/servers/slapd/overlays/dds.c
+++ b/servers/slapd/overlays/dds.c
@@ -1821,6 +1821,12 @@ slap_exop_refresh(
 	op->o_req_dn = op->o_req_ndn;
 
 	op->o_bd = select_backend( &op->o_req_ndn, 0 );
+	if ( op->o_bd == NULL ) {
+		send_ldap_error( op, rs, LDAP_NO_SUCH_OBJECT,
+			"no global superior knowledge" );
+		goto done;
+	}
+
 	if ( !SLAP_DYNAMIC( op->o_bd ) ) {
 		send_ldap_error( op, rs, LDAP_UNAVAILABLE_CRITICAL_EXTENSION,
 			"backend does not support dynamic directory services" );
diff --git a/servers/slapd/overlays/pcache.c b/servers/slapd/overlays/pcache.c
index db36896b44958ea3e9c223028ee30728aa2da62e..46ce69ce695195a4f48b89b2be637c6bae38074b 100644
--- a/servers/slapd/overlays/pcache.c
+++ b/servers/slapd/overlays/pcache.c
@@ -5111,6 +5111,10 @@ pcache_exop_query_delete(
 	op->o_req_dn = op->o_req_ndn;
 
 	op->o_bd = select_backend( &op->o_req_ndn, 0 );
+	if ( op->o_bd == NULL ) {
+		send_ldap_error( op, rs, LDAP_NO_SUCH_OBJECT,
+			"no global superior knowledge" );
+	}
 	rs->sr_err = backend_check_restrictions( op, rs,
 		(struct berval *)&pcache_exop_QUERY_DELETE );
 	if ( rs->sr_err != LDAP_SUCCESS ) {