diff --git a/.github/workflows/ci_test.yml b/.github/workflows/ci_test.yml
index cdc4ff4..af8231a 100644
--- a/.github/workflows/ci_test.yml
+++ b/.github/workflows/ci_test.yml
@@ -23,11 +23,11 @@
           repository: KorAP/Koral
           path: Koral
 
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: 'temurin'
-          java-version: 17
+          java-version: 21
           cache: 'maven'
 
 
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 45dff3a..68208fb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,4 +1,4 @@
-image: maven:3-eclipse-temurin-17-alpine
+image: maven:3-eclipse-temurin-21-alpine
 
 stages:
     - build
diff --git a/Changes b/Changes
index 327ecf7..359eec3 100644
--- a/Changes
+++ b/Changes
@@ -1,3 +1,6 @@
+0.64.5 2025-11-14
+    - [maintenance] Update to Java 21 (diewald)
+
 0.64.4 2025-09-17
     - [feature] Added --progress option to Krill-Indexer (kupietz)
     - [bugfix] Fixed vc cache tests (kupietz)
diff --git a/Readme.md b/Readme.md
index 3e7ca99..5fef687 100644
--- a/Readme.md
+++ b/Readme.md
@@ -46,7 +46,7 @@
 
 ## Prerequisites
 
-Java 17 (OpenJDK or Oracle JDK),
+Java 21 (OpenJDK or Oracle JDK),
 [Git](http://git-scm.com/),
 [Maven 3](https://maven.apache.org/).
 Further dependencies are resolved using Maven.
diff --git a/pom.xml b/pom.xml
index 5cc8cba..78392f6 100644
--- a/pom.xml
+++ b/pom.xml
@@ -59,7 +59,7 @@
   </developers>
 
   <properties>
-    <java.version>17</java.version>
+    <java.version>21</java.version>
     <jersey.version>3.1.11</jersey.version>
     <log4j.version>2.25.2</log4j.version>
     <jackson.version>2.18.1</jackson.version>