diff --git a/README.md b/README.md
index 63c0c07..1f8a42b 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,10 @@ This action installs Redmine and sets up an environment to run tests. It is prim
 
 See also [action.yml](./action.yml).
 
+## Supported Redmine version
+
+v4.2 or later
+
 ## Example
 
 ### Setting up [RedMica](https://github.com/redmica/redmica)
diff --git a/action.yml b/action.yml
index e767c81..fbe70d3 100644
--- a/action.yml
+++ b/action.yml
@@ -51,6 +51,16 @@ runs:
       env:
         REDMINE_DIR: ${{ inputs.path }}
 
+    - name: Check if the Redmine version is supported
+      run: |
+        if [ $redmine_version_number -lt $MINIUMUM_SUPPORTED_REDMINE_VERSION ]; then
+          echo "Redmine version $REDMINE_VERSION is not supported."
+          exit 1
+        fi
+      shell: bash
+      env:
+        MINIUMUM_SUPPORTED_REDMINE_VERSION: "420" # v4.2.0
+
     - name: Set up base environment
       run: |
         setup_base_for_major_version="setup-base-$REDMINE_VERSION_MAJOR.$REDMINE_VERSION_MINOR.sh"
diff --git a/scripts/set-version-envs.sh b/scripts/set-version-envs.sh
index f7d2b72..eb91be9 100755
--- a/scripts/set-version-envs.sh
+++ b/scripts/set-version-envs.sh
@@ -9,9 +9,24 @@ version_minor=$(grep -oE 'MINOR *= *[0-9]+' $file | awk 'NR==1 {print $3}')
 version_tiny=$(grep -oE 'TINY *= *[0-9]+' $file | awk 'NR==1 {print $3}')
 version_branch=$(grep -oE 'BRANCH *= *'\''.+?' $file | awk -F"'" 'NR==1 {print $2}')
 
-echo "Redmine Version: $version_major.$version_minor.$version_tiny.$version_branch"
+redmine_version=$version_major.$version_minor.$version_tiny.$version_branch
+redmine_version_number=$version_major$version_minor$version_tiny
 
+# v5.1.3.stable -> 5.1.3.stable
+echo "REDMINE_VERSION=$redmine_version" >> $GITHUB_ENV
+
+# v5.1.3.stable -> 5
 echo "REDMINE_VERSION_MAJOR=$version_major" >> $GITHUB_ENV
+# v5.1.3.stable -> 1
 echo "REDMINE_VERSION_MINOR=$version_minor" >> $GITHUB_ENV
+# v5.1.3.stable -> 3
 echo "REDMINE_VERSION_TINY=$version_tiny" >> $GITHUB_ENV
+# v5.1.3.stable -> stable
 echo "REDMINE_VERSION_BRANCH=$version_branch" >> $GITHUB_ENV
+
+# v5.1.3.stable -> 513
+echo "REDMINE_VERSION_NUMNER=$redmine_version_number" >> $GITHUB_ENV
+
+# Output version information
+echo "Redmine Version: $redmine_version"
+echo "Redmine Version Number: $redmine_version_number"