diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d1705b2..82d0d37 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -22,11 +22,11 @@ jobs:
       matrix:
         include:
           - redmine-repository: "redmine/redmine"
-            redmine-version: "4.2-stable"
+            redmine-version: "6.0-stable"
             redmine-database: "sqlite3"
-            ruby-version: "2.7"
+            ruby-version: "3.3"
             expected-about-db-adapter: "SQLite"
-            expected-about-redmine-version: '4\.2\.[0-9]\+\.stable'
+            expected-about-redmine-version: '6\.0\.[0-9]\+\.stable'
 
           - redmine-repository: "redmine/redmine"
             redmine-version: "5.1-stable"
@@ -35,13 +35,6 @@ jobs:
             expected-about-db-adapter: "Mysql2"
             expected-about-redmine-version: '5\.1\.[0-9]\+\.stable'
 
-          - redmine-repository: "redmica/redmica"
-            redmine-version: "stable-2.0"
-            redmine-database: "postgres:10"
-            ruby-version: "2.7"
-            expected-about-db-adapter: "PostgreSQL"
-            expected-about-redmine-version: '2\.0\.[0-9]\+\.stable'
-
           - redmine-repository: "redmica/redmica"
             redmine-version: "stable-3.0"
             redmine-database: "postgres:14"
@@ -84,8 +77,7 @@ jobs:
         run: bin/rails test test/unit/news_test.rb
         working-directory: ${{ env.REDMINE_SRC }}
 
-      - name: Run system test if Redmine >= 5.0
-        if: ${{ env.REDMINE_VERSION_MAJOR >= 5 }}
+      - name: Run system test
         run: bin/rails test test/system/my_page_test.rb
         working-directory: ${{ env.REDMINE_SRC }}
 
diff --git a/README.md b/README.md
index 1f8a42b..dcb4e54 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ See also [action.yml](./action.yml).
 
 ## Supported Redmine version
 
-v4.2 or later
+v5.0 or later
 
 ## Example
 
@@ -39,10 +39,10 @@ v4.2 or later
 ```yaml
 - uses: hidakatsuya/action-setup-redmine@v1
   with:
-    repository: 'redmica/redmica'
-    version: 'v2.4.2'
+    repository: 'redmine/redmine'
+    version: 'v6.0.1'
     database: 'postgres:14'
-    ruby-version: '3.2'
+    ruby-version: '3.3'
 ```
 
 ### Run a test for the Redmine plugin
diff --git a/action.yml b/action.yml
index 8ed1b32..64b9266 100644
--- a/action.yml
+++ b/action.yml
@@ -59,7 +59,7 @@ runs:
         fi
       shell: bash
       env:
-        MINIUMUM_SUPPORTED_REDMINE_VERSION: "402" # v4.2.x
+        MINIUMUM_SUPPORTED_REDMINE_VERSION: "500" # v5.0.0
 
     - name: Set up base environment
       run: $GITHUB_ACTION_PATH/scripts/setup-base.sh
diff --git a/scripts/setup-base-4.2.sh b/scripts/setup-base-6.0.sh
similarity index 84%
rename from scripts/setup-base-4.2.sh
rename to scripts/setup-base-6.0.sh
index 7490079..806b0b1 100755
--- a/scripts/setup-base-4.2.sh
+++ b/scripts/setup-base-6.0.sh
@@ -21,7 +21,3 @@ echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" | sud
 sudo apt-get update
 sudo apt-get install -y --no-install-recommends google-chrome-stable
 echo GOOGLE_CHROME_OPTS_ARGS="headless,disable-gpu,no-sandbox,disable-dev-shm-usage" >> $GITHUB_ENV
-
-# Fix LoadError cannot load such file -- builder
-# https://www.redmine.org/issues/40802
-echo "gem 'builder', '~> 3.2.4'" >> $REDMINE_DIR/Gemfile.local
diff --git a/scripts/setup-base.sh b/scripts/setup-base.sh
index aa16eff..561d8a8 100755
--- a/scripts/setup-base.sh
+++ b/scripts/setup-base.sh
@@ -6,9 +6,9 @@ set -eu
 major_version_with_branch=$REDMINE_VERSION_MAJOR.$REDMINE_VERSION_MINOR.$REDMINE_VERSION_BRANCH
 
 case $major_version_with_branch in
-    5.1.devel)
+    6.0.devel)
         setup_version="next";;
-    5.1*|5.0*|4.2*)
+    6.0*|5.1*|5.0*)
         setup_version="$REDMINE_VERSION_MAJOR.$REDMINE_VERSION_MINOR";;
     *)
         setup_version="next";;