diff --git a/.github/workflows/build-test-deploy.yml b/.github/workflows/build-test-deploy.yml
index b375801e97..deb5a2c193 100644
--- a/.github/workflows/build-test-deploy.yml
+++ b/.github/workflows/build-test-deploy.yml
@@ -17,7 +17,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  JAVA_VERSION: '17'
+  JAVA_VERSION: '21'
   CONTAINER_REGISTRY_URL: 'ghcr.io/infonl'
   APPLICATION_NAME: 'zaakafhandelcomponent'
 
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 1b8b66b5f8..20a25c2874 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -16,7 +16,7 @@ on:
     - cron: "21 11 * * 0"
 
 env:
-  JAVA_VERSION: "17"
+  JAVA_VERSION: "21"
 
 jobs:
   analyze:
diff --git a/Dockerfile b/Dockerfile
index 54d2d454e9..a8c0717264 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 ### Create runtime image fase
-FROM docker.io/eclipse-temurin:17-jre-focal as runtime
+FROM docker.io/eclipse-temurin:21-jre-alpine as runtime
 
 # Import certificates into Java truststore
 ADD certificates /certificates
@@ -12,7 +12,7 @@ RUN keytool -importcert -cacerts -alias Staat_der_Nederlanden_Private_Services_C
 COPY target/zaakafhandelcomponent.jar /
 
 # Copy build timestamp (used by HealthCheckService.java)
-RUN date --iso-8601='seconds' > /build_timestamp.txt
+RUN date -Iseconds > /build_timestamp.txt
 
 # Start zaakafhandelcomponent
 ENTRYPOINT ["java", "--enable-preview", "-jar", "zaakafhandelcomponent.jar"]
diff --git a/build.gradle.kts b/build.gradle.kts
index de221d17c2..f2ebb4d91b 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -34,8 +34,9 @@ repositories {
 group = "net.atos.common-ground"
 description = "Zaakafhandelcomponent"
 
-// we will only upgrade Java when WildFly explicitly supports a new version
-val javaVersion = JavaVersion.VERSION_17
+// make sure the Java version is supported by WildFly
+// and update our base Docker image and JDK versions in our GitHubs workflows accordingly
+val javaVersion = JavaVersion.VERSION_21
 
 val zacDockerImage by extra {
     if (project.hasProperty("zacDockerImage")) {
@@ -166,7 +167,7 @@ detekt {
 }
 
 jacoco {
-    toolVersion = "0.8.7"
+    toolVersion = "0.8.11"
 }
 
 java {
@@ -301,7 +302,6 @@ tasks {
 
     withType<JavaCompile> {
         options.encoding = "UTF-8"
-        options.compilerArgs.add("--enable-preview")
     }
 
     withType<org.openapitools.generator.gradle.plugin.tasks.GenerateTask> {
diff --git a/docs/development/INSTALL.md b/docs/development/INSTALL.md
index 1bec48716f..ac0dcfb345 100644
--- a/docs/development/INSTALL.md
+++ b/docs/development/INSTALL.md
@@ -7,7 +7,7 @@ General ZAC usage instructions may be found in the [README.md](../../README.md)
 
 ### Prerequisites
 
-- Java JDK 17 (we use the `Temurin` distribution)
+- Java JDK 21 (we use the `Temurin` distribution)
 
 ### Gradle build
 
@@ -72,7 +72,7 @@ When opening the ZAC project in IntelliJ make sure to select 'Open as Gradle pro
 #### Prerequisites
 
 First you will need to set up IntelliJ for ZAC:
-1. Install and use JDK 17 (we use the `Temurin` distribution).
+1. Install and use the correct JDK distribution (see above).
 2. Follow the [local WildFly instructions](../../scripts/wildfly/README.md) and install `WildFly`.
 3. Enable the built-in IntelliJ WildFly extension if not already enabled (note that this requires the IntelliJ Enterprise Edition).
 4. Create a run configuration using the WildFly extension for ZAC using the `JBoss/Wildfly Server - local` template.
diff --git a/src/main/java/net/atos/zac/app/klanten/converter/RESTPersoonConverter.java b/src/main/java/net/atos/zac/app/klanten/converter/RESTPersoonConverter.java
index fd01ecea8a..b882978d6e 100644
--- a/src/main/java/net/atos/zac/app/klanten/converter/RESTPersoonConverter.java
+++ b/src/main/java/net/atos/zac/app/klanten/converter/RESTPersoonConverter.java
@@ -201,9 +201,9 @@ private String convertGeboortedatum(final AbstractDatum abstractDatum) {
 
     private String convertVerblijfplaats(final AbstractVerblijfplaats abstractVerblijfplaats) {
         return switch (abstractVerblijfplaats) {
-            case Adres adres && adres.getVerblijfadres() != null ->
+            case Adres adres when adres.getVerblijfadres() != null ->
                     convertVerblijfadresBinnenland(adres.getVerblijfadres());
-            case VerblijfplaatsBuitenland verblijfplaatsBuitenland && verblijfplaatsBuitenland.getVerblijfadres() != null ->
+            case VerblijfplaatsBuitenland verblijfplaatsBuitenland when verblijfplaatsBuitenland.getVerblijfadres() != null ->
                     convertVerblijfadresBuitenland(verblijfplaatsBuitenland.getVerblijfadres());
             case VerblijfplaatsOnbekend verblijfplaatsOnbekend -> ONBEKEND;
             default -> null;
diff --git a/src/main/java/net/atos/zac/mailtemplates/MailTemplateHelper.java b/src/main/java/net/atos/zac/mailtemplates/MailTemplateHelper.java
index 856f6174fd..7f3666f3d6 100644
--- a/src/main/java/net/atos/zac/mailtemplates/MailTemplateHelper.java
+++ b/src/main/java/net/atos/zac/mailtemplates/MailTemplateHelper.java
@@ -278,8 +278,8 @@ private static String replaceInitiatorVariabelenResultaatItem(final String resol
 
     private static String convertAdres(final Persoon persoon) {
         return switch (persoon.getVerblijfplaats()) {
-            case Adres adres && adres.getVerblijfadres() != null -> convertAdres(adres.getVerblijfadres());
-            case VerblijfplaatsBuitenland verblijfplaatsBuitenland && verblijfplaatsBuitenland.getVerblijfadres() != null ->
+            case Adres adres when adres.getVerblijfadres() != null -> convertAdres(adres.getVerblijfadres());
+            case VerblijfplaatsBuitenland verblijfplaatsBuitenland when verblijfplaatsBuitenland.getVerblijfadres() != null ->
                     convertAdres(verblijfplaatsBuitenland.getVerblijfadres());
             default -> EMPTY;
         };