diff --git a/src/zfw_xdp_dns_filter.c b/src/zfw_xdp_dns_filter.c
index 10c41fa..5732127 100644
--- a/src/zfw_xdp_dns_filter.c
+++ b/src/zfw_xdp_dns_filter.c
@@ -142,7 +142,7 @@ int xdp_filter(struct xdp_md *ctx) {
                 }
             }
             long ret = set_dns(i, dns_payload);
-            if (ret < 0){
+            if (ret > 0){
                bpf_printk("wrote %d characters", ret);
             }
             dns_payload = (dns_payload + dns_name_len + 4);