diff --git a/servers/slapd/back-bdb2/modify.c b/servers/slapd/back-bdb2/modify.c
index 8da3a396ae..ef263e7ed6 100644
--- a/servers/slapd/back-bdb2/modify.c
+++ b/servers/slapd/back-bdb2/modify.c
@@ -314,7 +314,9 @@ bdb2i_replace_values(
 {
 	(void) attr_delete( &e->e_attrs, mod->mod_type );
 
-	if ( attr_merge( e, mod->mod_type, mod->mod_bvalues ) != 0 ) {
+	if ( mod->bvalues != NULL &&
+		attr_merge( e, mod->mod_type, mod->mod_bvalues ) != 0 )
+	{
 		return( LDAP_CONSTRAINT_VIOLATION );
 	}
 
diff --git a/servers/slapd/back-ldbm/modify.c b/servers/slapd/back-ldbm/modify.c
index 41197e0513..6f58b94767 100644
--- a/servers/slapd/back-ldbm/modify.c
+++ b/servers/slapd/back-ldbm/modify.c
@@ -346,7 +346,9 @@ replace_values(
 {
 	(void) attr_delete( &e->e_attrs, mod->mod_type );
 
-	if ( attr_merge( e, mod->mod_type, mod->mod_bvalues ) != 0 ) {
+	if ( mod->mod_bvalues != NULL &&
+		attr_merge( e, mod->mod_type, mod->mod_bvalues ) != 0 )
+	{
 		return( LDAP_CONSTRAINT_VIOLATION );
 	}