diff --git a/app/controllers/repp/v1/registrar/nameservers_controller.rb b/app/controllers/repp/v1/registrar/nameservers_controller.rb
index 5ce44caa2..0d03bf2a9 100644
--- a/app/controllers/repp/v1/registrar/nameservers_controller.rb
+++ b/app/controllers/repp/v1/registrar/nameservers_controller.rb
@@ -13,8 +13,8 @@ module Repp
                                                        'nameserver replacement'
           param :attributes, Hash, required: true, desc: 'Object holding new nameserver values' do
             param :hostname, String, required: true, desc: 'New hostname of nameserver'
-            param :ipv4, Array, required: false, desc: 'Array of fixed IPv4 addresses'
-            param :ipv6, Array, required: false, desc: 'Array of fixed IPv6 addresses'
+            param :ipv4, Array, of: String, required: false, desc: 'Array of fixed IPv4 addresses'
+            param :ipv6, Array, of: String, required: false, desc: 'Array of fixed IPv6 addresses'
           end
         end
         def update
diff --git a/test/integration/repp/v1/registrar/nameservers_test.rb b/test/integration/repp/v1/registrar/nameservers_test.rb
index e58e4651c..102649637 100644
--- a/test/integration/repp/v1/registrar/nameservers_test.rb
+++ b/test/integration/repp/v1/registrar/nameservers_test.rb
@@ -95,7 +95,7 @@ class ReppV1RegistrarNameserversTest < ActionDispatch::IntegrationTest
 
     assert_response :bad_request
     assert_equal 2005, json[:code]
-    assert_equal 'IPv4 should be array [ipv4]', json[:message]
+    assert json[:message].include? 'Must be an array of String'
   end
 
   def test_ipv6_isnt_array
@@ -118,7 +118,7 @@ class ReppV1RegistrarNameserversTest < ActionDispatch::IntegrationTest
 
     assert_response :bad_request
     assert_equal 2005, json[:code]
-    assert_equal 'IPv6 should be array [ipv6]', json[:message]
+    assert json[:message].include? 'Must be an array of String'
   end
 
   def test_bulk_nameservers_change_in_array_of_domains