diff --git a/.codeclimate.yml b/.codeclimate.yml
index b193156a..0bceeb0f 100644
--- a/.codeclimate.yml
+++ b/.codeclimate.yml
@@ -41,4 +41,4 @@ plugins:
   sonar-java:
     enabled: true
     config:
-      sonar.java.source: 21
+      sonar.java.source: 17
diff --git a/.deepsource.toml b/.deepsource.toml
index 94e8f41d..f4160b65 100644
--- a/.deepsource.toml
+++ b/.deepsource.toml
@@ -15,4 +15,4 @@ name = "java"
 enabled = true
 
   [analyzers.meta]
-  runtime_version = "21"
+  runtime_version = "17"
diff --git a/.github/workflows/maven-verify.yml b/.github/workflows/maven-verify.yml
index fd7d49f0..b5d9f08c 100644
--- a/.github/workflows/maven-verify.yml
+++ b/.github/workflows/maven-verify.yml
@@ -17,7 +17,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v5
         with:
-          java-version: '21'
+          java-version: '17'
           distribution: 'adopt'
       - name: Cache SonarQube packages
         uses: actions/cache@v6
@@ -73,6 +73,22 @@ jobs:
           if-no-files-found: error
           include-hidden-files: true
 
+  forward-compatibility:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java-version: ['21', '25']
+    steps:
+      - uses: actions/checkout@v7
+      - name: Set up JDK ${{ matrix.java-version }}
+        uses: actions/setup-java@v5
+        with:
+          java-version: ${{ matrix.java-version }}
+          distribution: 'adopt'
+          cache: 'maven'
+      - name: Run tests on JDK ${{ matrix.java-version }}
+        run: mvn -B -ntp test
+
   generate-docs:
     runs-on: ubuntu-latest
     needs: verify
diff --git a/AGENTS.md b/AGENTS.md
index 9762edc4..4402ccd3 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -30,7 +30,7 @@ manually.
 
 | Concern | Technology |
 |---|---|
-| Language | Java 21 |
+| Language | Java 17 minimum runtime; CI also tests Java 21 and 25 |
 | Build | Apache Maven (multi-module) |
 | Unit tests | JUnit 5 (`junit-jupiter` 5.11.4) |
 | Assertions | Hamcrest 3.0 |
diff --git a/README.md b/README.md
index daed02f9..129f273d 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,8 @@ This project is divided into multiple maven module
 
 ## Adding the dependency
 
+MetarParser requires Java 17 or later.
+
 To add the service module :
 
 ```xml
diff --git a/pom.xml b/pom.xml
index a183d24b..6e52d16e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -44,8 +44,7 @@
     </licenses>
 
     <properties>
-        <maven.compiler.source>21</maven.compiler.source>
-        <maven.compiler.target>21</maven.compiler.target>
+        <maven.compiler.release>17</maven.compiler.release>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <jacoco.coverage.instruction.minimum>0.98</jacoco.coverage.instruction.minimum>
         <jacoco.coverage.branch.minimum>0.96</jacoco.coverage.branch.minimum>