diff --git a/.github/workflows/spec.yml b/.github/workflows/spec.yml
index e580173..6c2ca8c 100644
--- a/.github/workflows/spec.yml
+++ b/.github/workflows/spec.yml
@@ -13,13 +13,9 @@ jobs:
   spec:
     strategy:
       matrix:
-        os: ['ubuntu-20.04', 'ubuntu-22.04']
+        os: ['ubuntu-22.04', 'ubuntu-24.04']
         ruby-version: ['3.1', '3.2', '3.3']
-        include:
-        - os: 'ubuntu-20.04'
-          ruby-version: '3.0'
     runs-on: ${{ matrix.os }}
-
     steps:
     - uses: actions/checkout@v3
     - name: Set up Ruby
diff --git a/spec/openid_connect/discovery/provider/config/resource_spec.rb b/spec/openid_connect/discovery/provider/config/resource_spec.rb
index 8ecfa2f..b1c92c2 100644
--- a/spec/openid_connect/discovery/provider/config/resource_spec.rb
+++ b/spec/openid_connect/discovery/provider/config/resource_spec.rb
@@ -9,7 +9,7 @@
   describe '#endpoint' do
     context 'when invalid host' do
       before do
-        resource.host = 'hoge*hoge'
+        resource.host = 'invalid:host'
       end
 
       it do