diff --git a/.github/workflows/deploy_snapshot.yml b/.github/workflows/deploy_snapshot.yml
index 17278ca..f755388 100644
--- a/.github/workflows/deploy_snapshot.yml
+++ b/.github/workflows/deploy_snapshot.yml
@@ -15,7 +15,7 @@ on:
     types: [ trigger_after_upstream_deploy ]
 
 env:
-  GRADLE_VERSION: 7.6 # Gradle version used
+  GRADLE_VERSION: 8.5 # Gradle version used
   GRADLE_CLI_OPTS: "-Pci --build-cache --refresh-dependencies" # CLI options passed to Gradle
   GRADLE_BUILD_ACTION_CACHE_KEY_JOB: "test-cache-${{ github.head_ref }}.${{ github.sha }}"
 
@@ -29,6 +29,11 @@ jobs:
     steps:
       - name: Checkout project sources
         uses: actions/checkout@v4
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: 21
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
         with:
@@ -45,6 +50,11 @@ jobs:
     steps:
       - name: Checkout project sources
         uses: actions/checkout@v4
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: 21
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
         with:
diff --git a/.github/workflows/test_branch.yml b/.github/workflows/test_branch.yml
index f401ba2..f9a00dc 100644
--- a/.github/workflows/test_branch.yml
+++ b/.github/workflows/test_branch.yml
@@ -12,7 +12,7 @@ on:
     branches-ignore: [ "dev" ] # Do not run this on the default branch
 
 env:
-  GRADLE_VERSION: 7.6 # Gradle version used
+  GRADLE_VERSION: 8.5 # Gradle version used
   GRADLE_CLI_OPTS: "-Pci --build-cache --refresh-dependencies" # CLI options passed to Gradle
   GRADLE_BUILD_ACTION_CACHE_KEY_JOB: "test-cache-${{ github.head_ref }}.${{ github.sha }}"
 
@@ -26,6 +26,11 @@ jobs:
     steps:
       - name: Checkout project sources
         uses: actions/checkout@v4
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: 21
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
         with:
diff --git a/build.gradle b/build.gradle
index 3659feb..4cc9284 100644
--- a/build.gradle
+++ b/build.gradle
@@ -5,11 +5,15 @@ plugins {
   id 'java-library'
   id 'maven-publish'
   id "de.monticore.generator" version "$mc_version" // MontiCore Plugin
-  id "com.github.johnrengelman.shadow" version "$shadow_plugin_version"
+  id "com.gradleup.shadow" version "$shadow_plugin_version"
   id 'jacoco'
   id "io.github.themrmilchmann.ecj" version "0.2.0"
 }
 
+ecj {
+  compilerVersion = "3.43.0"
+}
+
 def grammarDir = "src/main/grammars"
 
 group = "de.monticore.lang"
@@ -31,7 +35,7 @@ sourceSets {
 
 java {
   toolchain {
-    languageVersion = JavaLanguageVersion.of(11)
+    languageVersion = JavaLanguageVersion.of(21)
   }
   // Deprecated feature, published for compatibility reasons
   registerFeature('grammars') {
diff --git a/gradle.properties b/gradle.properties
index c83f8ba..d44a4e2 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -5,7 +5,7 @@ mc_version=7.9.0-SNAPSHOT
 mlc_version=7.8.0-SNAPSHOT
 version=7.9.0-SNAPSHOT
 useLocalRepo=false
-shadow_plugin_version=7.1.2
+shadow_plugin_version=8.3.9
 guava_version=33.5.0-jre
 commons_lang3_version=3.20.0
 commons_cli_version=1.11.0