diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
index 9ce53b9..58d5f3e 100644
--- a/src/core/ngx_resolver.c
+++ b/src/core/ngx_resolver.c
@@ -1798,6 +1798,12 @@
     i = sizeof(ngx_resolver_hdr_t);
 
     while (i < (ngx_uint_t) n) {
+
+        if (buf[i] & 0xc0) {
+            err = "unexpected compression pointer in DNS response";
+            goto done;
+        }
+
         if (buf[i] == '\0') {
             goto found;
         }