diff --git a/src/main/java/codes/thischwa/dyndrest/ApiController.java b/src/main/java/codes/thischwa/dyndrest/ApiController.java
index 59cf55c..1cd4b50 100644
--- a/src/main/java/codes/thischwa/dyndrest/ApiController.java
+++ b/src/main/java/codes/thischwa/dyndrest/ApiController.java
@@ -125,7 +125,7 @@ public ResponseEntity<IpSetting> info(String host, @RequestParam String apitoken
   }
 
   @Override
-  public ResponseEntity<Object> addZone(String name, String ns) {
+  public ResponseEntity<String> addZone(String name, String ns) {
     log.debug("entered #addZone: name={}, ns={}", name, ns);
     if (!domainNameValidator.isValidDomainNames(name, ns)) {
       log.error("Domain name ({}) or nameserver ({}) is malformed.", name, ns);
diff --git a/src/main/java/codes/thischwa/dyndrest/ApiRoutes.java b/src/main/java/codes/thischwa/dyndrest/ApiRoutes.java
index f2a1e1a..d3f0f0c 100644
--- a/src/main/java/codes/thischwa/dyndrest/ApiRoutes.java
+++ b/src/main/java/codes/thischwa/dyndrest/ApiRoutes.java
@@ -128,7 +128,7 @@ ResponseEntity<IpSetting> info(
           String apitoken);
 
   @GetMapping(value = "/zone/add/{name}/{ns}", produces = MediaType.TEXT_PLAIN_VALUE)
-  ResponseEntity<Object> addZone(
+  ResponseEntity<String> addZone(
       @Parameter(
               description = "The name of the zone, must be a valid domain name.",
               content = @Content(mediaType = MediaType.TEXT_PLAIN_VALUE),