diff --git a/libraries/liblber/memory.c b/libraries/liblber/memory.c
index 614305c9ed..ddd78622f2 100644
--- a/libraries/liblber/memory.c
+++ b/libraries/liblber/memory.c
@@ -700,8 +700,9 @@ struct berval *
 ber_bvreplace_x( struct berval *dst, LDAP_CONST struct berval *src, void *ctx )
 {
 	assert( dst != NULL );
+	assert( !BER_BVISNULL( src ) );
 
-	if ( dst->bv_len == 0 || dst->bv_len < src->bv_len ) {
+	if ( BER_BVISNULL( dst ) || dst->bv_len < src->bv_len ) {
 		dst->bv_val = ber_memrealloc_x( dst->bv_val, src->bv_len + 1, ctx );
 	}