diff --git a/app/models/dnskey.rb b/app/models/dnskey.rb
index 2d1634680..ee0727c0a 100644
--- a/app/models/dnskey.rb
+++ b/app/models/dnskey.rb
@@ -4,11 +4,13 @@ class Dnskey < ActiveRecord::Base
   belongs_to :domain
 
   validate :validate_algorithm
+  validate :validate_protocol
 
   def epp_code_map
     {
       '2005' => [
-        [:alg, :invalid, { value: { obj: 'alg', val: alg } }]
+        [:alg, :invalid, { value: { obj: 'alg', val: alg } }],
+        [:protocol, :invalid, { value: { obj: 'protocol', val: protocol } }],
       ],
       '2306' => [
         [:ipv4, :blank]
@@ -16,10 +18,13 @@ class Dnskey < ActiveRecord::Base
     }
   end
 
-
   def validate_algorithm
     return if %w(3 5 6 7 8 252 253 254 255).include?(alg.to_s)
     errors.add(:alg, :invalid)
-    # , format: {with: /3|5|6/, message: :alg_invalid}
+  end
+
+  def validate_protocol
+    return if %w(3).include?(protocol.to_s)
+    errors.add(:protocol, :invalid)
   end
 end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index bdd8949d9..5fc95e1fc 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -187,6 +187,8 @@ en:
           attributes:
             alg:
               invalid: 'Algorithm is invalid'
+            protocol:
+              invalid: 'Protocol is invalid'
 
     attributes:
       epp_domain: &epp_domain_attributes
diff --git a/spec/epp/domain_spec.rb b/spec/epp/domain_spec.rb
index 95ccf1c9b..47930e4ce 100644
--- a/spec/epp/domain_spec.rb
+++ b/spec/epp/domain_spec.rb
@@ -372,7 +372,7 @@ describe 'EPP Domain', epp: true do
             {
               dnskey: {
                 flags: { value: '257' },
-                protocol: { value: '3' },
+                protocol: { value: '4' },
                 alg: { value: '9' },
                 pubKey: { value: 'AwEAAddt2AkLfYGKgiEZB5SmIF8EvrjxNMH6HtxWEA4RJ9Ao6LCWheg8' }
               }
@@ -388,7 +388,7 @@ describe 'EPP Domain', epp: true do
             {
               dnskey: {
                 flags: { value: '256' },
-                protocol: { value: '3' },
+                protocol: { value: '5' },
                 alg: { value: '254' },
                 pubKey: { value: '841936717ae427ace63c28d04918569a841936717ae427ace63c28d0' }
               }
@@ -397,12 +397,19 @@ describe 'EPP Domain', epp: true do
         })
 
         response = epp_request(xml, :xml)
+        po response
 
         expect(response[:results][0][:msg]).to eq('Algorithm is invalid')
         expect(response[:results][0][:value]).to eq('9')
-        expect(response[:results][1][:msg]).to eq('Algorithm is invalid')
-        expect(response[:results][1][:value]).to eq('10')
-        po response
+
+        expect(response[:results][1][:msg]).to eq('Protocol is invalid')
+        expect(response[:results][1][:value]).to eq('4')
+
+        expect(response[:results][2][:msg]).to eq('Algorithm is invalid')
+        expect(response[:results][2][:value]).to eq('10')
+
+        expect(response[:results][3][:msg]).to eq('Protocol is invalid')
+        expect(response[:results][3][:value]).to eq('5')
       end
     end