diff --git a/.ci/build.sh b/.ci/build.sh
index 9016954290..ae7280b1b3 100755
--- a/.ci/build.sh
+++ b/.ci/build.sh
@@ -19,7 +19,7 @@ function build() {
             pmd_ci_log_info "Install openjdk17 for integration tests and pmd-regression-tests"
             pmd_ci_openjdk_install_adoptium 17
             pmd_ci_log_info "Install openjdk21 for integration tests and pmd-regression-tests"
-            pmd_ci_openjdk_install_adoptium "21-ea"
+            pmd_ci_openjdk_install_adoptium 21
             PMD_MAVEN_EXTRA_OPTS=(
                 -Djava8.home="${HOME}/openjdk8"
                 -Djava17.home="${HOME}/openjdk17"
diff --git a/docs/pages/release_notes.md b/docs/pages/release_notes.md
index a892d43832..d58ec15d53 100644
--- a/docs/pages/release_notes.md
+++ b/docs/pages/release_notes.md
@@ -49,6 +49,8 @@ The remaining section describes the complete release notes for 7.0.0.
 
 #### Fixed issues
 
+* miscellaneous
+  * [#4699](https://github.com/pmd/pmd/pull/4699):   Make PMD buildable with java 21
 * java-codestyle
   * [#2847](https://github.com/pmd/pmd/issues/2847): \[java] New Rule: Use Explicit Types
   * [#4578](https://github.com/pmd/pmd/issues/4578): \[java] CommentDefaultAccessModifier comment needs to be before annotation if present
@@ -395,6 +397,7 @@ See also [Detailed Release Notes for PMD 7]({{ baseurl }}pmd_release_notes_pmd7.
     * [#4460](https://github.com/pmd/pmd/pull/4460):   Fix assembly-plugin warnings
     * [#4582](https://github.com/pmd/pmd/issues/4582): \[dist] Download link broken
     * [#4691](https://github.com/pmd/pmd/issues/4691): \[CVEs] Critical and High CEVs reported on PMD and PMD dependencies
+    * [#4699](https://github.com/pmd/pmd/pull/4699):   Make PMD buildable with java 21
 * ant
     * [#4080](https://github.com/pmd/pmd/issues/4080): \[ant] Split off Ant integration into a new submodule
 * core
diff --git a/pom.xml b/pom.xml
index 8245e6c548..ef6b71625d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -842,6 +842,23 @@
                 <scope>test</scope>
             </dependency>
 
+            <!-- byte-buddy is used by mockito.
+                 Using a newer version than the one from mockito 4.11.0 for Java 21 compatibility
+                 At least byte-buddy 1.14.3 is required for Java 21.
+            -->
+            <dependency>
+                <groupId>net.bytebuddy</groupId>
+                <artifactId>byte-buddy</artifactId>
+                <version>1.14.9</version>
+                <scope>test</scope>
+            </dependency>
+            <dependency>
+                <groupId>net.bytebuddy</groupId>
+                <artifactId>byte-buddy-agent</artifactId>
+                <version>1.14.9</version>
+                <scope>test</scope>
+            </dependency>
+
             <dependency>
                 <groupId>com.github.tomakehurst</groupId>
                 <artifactId>wiremock-jre8</artifactId>