diff --git a/dnsapi/dns_hostup.sh b/dnsapi/dns_hostup.sh
index 4da0dd9d..8d0600f7 100644
--- a/dnsapi/dns_hostup.sh
+++ b/dnsapi/dns_hostup.sh
@@ -182,9 +182,10 @@ _hostup_detect_zone() {
       return 0
     fi
 
-    if ! printf "%s" "$_domain_candidate" | _contains "."; then
-      break
-    fi
+    case "$_domain_candidate" in
+      *.*) ;;
+      *) break ;;
+    esac
 
     _domain_candidate="${_domain_candidate#*.}"
   done