diff --git a/tools/lib/bpf/nlattr.c b/tools/lib/bpf/nlattr.c
index 1e69c0c8d413..e610becd03e8 100644
--- a/tools/lib/bpf/nlattr.c
+++ b/tools/lib/bpf/nlattr.c
@@ -177,7 +177,7 @@ int libbpf_nla_dump_errormsg(struct nlmsghdr *nlh)
 		hlen += nlmsg_len(&err->msg);
 
 	attr = (struct nlattr *) ((void *) err + hlen);
-	alen = nlh->nlmsg_len - hlen;
+	alen = (void *)nlh + nlh->nlmsg_len - (void *)attr;
 
 	if (libbpf_nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen,
 			     extack_policy) != 0) {