diff --git a/lib/github-pages-health-check/domain.rb b/lib/github-pages-health-check/domain.rb
index 32e2e22..8063dc4 100644
--- a/lib/github-pages-health-check/domain.rb
+++ b/lib/github-pages-health-check/domain.rb
@@ -356,7 +356,6 @@ def served_by_pages?
         return unless dns_resolves?
 
         @served_by_pages = begin
-          return false unless response.mock? || response.return_code == :ok
           return true if response.headers["Server"] == "GitHub.com"
 
           # Typhoeus mangles the case of the header, compare insensitively
diff --git a/lib/github-pages-health-check/version.rb b/lib/github-pages-health-check/version.rb
index 3d580b5..726dc7b 100644
--- a/lib/github-pages-health-check/version.rb
+++ b/lib/github-pages-health-check/version.rb
@@ -2,6 +2,6 @@
 
 module GitHubPages
   module HealthCheck
-    VERSION = "1.17.1"
+    VERSION = "1.17.2"
   end
 end
diff --git a/spec/github_pages_health_check/domain_spec.rb b/spec/github_pages_health_check/domain_spec.rb
index f57e0a7..5372852 100644
--- a/spec/github_pages_health_check/domain_spec.rb
+++ b/spec/github_pages_health_check/domain_spec.rb
@@ -483,6 +483,12 @@
       allow(subject).to receive(:dns) { [a_packet] }
       stub_request(:head, domain)
         .to_return(:status => status, :headers => headers)
+
+      stub_request(:head, "https://githubuniverse.com/")
+        .to_return(:status => 200, :headers => { :server => "GitHub.com" })
+
+      stub_request(:head, "https://github.com/login")
+        .to_return(:status => 200, :headers => { :server => "GitHub.com" })
     end
 
     context "with the Pages server header" do
@@ -507,6 +513,27 @@
           expect(subject).to be_served_by_pages
         end
       end
+
+      context "an alternate domain" do
+        let(:domain) { "http://www.githubuniverse.com" }
+        let(:status) { 301 }
+        let(:headers) { { :location => "https://githubuniverse.com" } }
+        before(:each) { allow(subject).to receive(:dns) { [cname_packet] } }
+
+        it "knows about domains that redirect to the primary domain on pages" do
+          expect(subject).to be_served_by_pages
+        end
+      end
+
+      context "a private page" do
+        let(:domain) { "http://private-page.githubapp.com" }
+        let(:status) { 302 }
+        let(:headers) { { :location => "https://github.com/login" } }
+
+        it "considers it valid if it redirects to github.com/login" do
+          expect(subject).to be_served_by_pages
+        end
+      end
     end
 
     context "with a request ID" do