diff --git a/rewrite.c b/rewrite.c
index b383103..b292374 100644
--- a/rewrite.c
+++ b/rewrite.c
@@ -464,6 +464,8 @@ int dorewritemodvattr(struct tlv *vendortlv, struct modattr *modvattr) {
     for (offset = 4; offset < vendortlv->l; offset += ATTRLEN(vendortlv->v+offset)) {
         if (ATTRTYPE(vendortlv->v+offset) == modvattr->t) {
             tmpattr = maketlv(ATTRTYPE(vendortlv->v+offset), ATTRVALLEN(vendortlv->v+offset), ATTRVAL(vendortlv->v+offset));
+            if (!tmpattr)
+                return 0;
             if (dorewritemodattr(tmpattr, modvattr)) {
                 int size_diff = tmpattr->l - ATTRVALLEN(vendortlv->v+offset);
                 int rem_size = vendortlv->l - offset - ATTRLEN(vendortlv->v+offset);