diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 2212a8fa..2d7b73bf 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -26,7 +26,7 @@ jobs:
         if: inputs.os == 'almalinux:9'
         with:
           distribution: 'temurin'
-          java-version: '11'
+          java-version: '21'
 
       - name: Install dependencies on Ubuntu 24.04
         if: inputs.os == 'ubuntu:24.04'
diff --git a/.github/workflows/create-release.yml b/.github/workflows/create-release.yml
index 206349ea..5e3a319d 100644
--- a/.github/workflows/create-release.yml
+++ b/.github/workflows/create-release.yml
@@ -60,7 +60,7 @@ jobs:
           mv libcobj/* opensourcecobol4j
       - uses: actions/setup-java@v4
         with:
-          java-version: '11'
+          java-version: '21'
           distribution: 'temurin'
       - name: Validate Gradle wrapper
         uses: gradle/wrapper-validation-action@v3
diff --git a/.github/workflows/static-analysis.yml b/.github/workflows/static-analysis.yml
index 8cef3aef..4614a523 100644
--- a/.github/workflows/static-analysis.yml
+++ b/.github/workflows/static-analysis.yml
@@ -18,7 +18,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'temurin'
-          java-version: '11'
+          java-version: '21'
 
       - name: Install static analysis tools
         run: |
diff --git a/.github/workflows/test-cobj-api.yml b/.github/workflows/test-cobj-api.yml
index 4f95c137..b1e282bf 100644
--- a/.github/workflows/test-cobj-api.yml
+++ b/.github/workflows/test-cobj-api.yml
@@ -30,7 +30,7 @@ jobs:
         if: inputs.os != 'amazonlinux:2023'
         with:
           distribution: 'temurin'
-          java-version: '11'
+          java-version: '21'
 
       - name: Install dependencies on Ubuntu 24.04
         if: inputs.os == 'ubuntu:24.04'
diff --git a/.github/workflows/test-nist.yml b/.github/workflows/test-nist.yml
index 3fbd8cd5..f593376c 100644
--- a/.github/workflows/test-nist.yml
+++ b/.github/workflows/test-nist.yml
@@ -40,7 +40,7 @@ jobs:
         if: inputs.os != 'amazonlinux:2023'
         with:
           distribution: 'temurin'
-          java-version: '11'
+          java-version: '21'
 
       - name: Install dependencies on Ubuntu 24.04
         if: inputs.os == 'ubuntu:24.04'
diff --git a/.github/workflows/test-other.yml b/.github/workflows/test-other.yml
index b7703654..caa83c62 100644
--- a/.github/workflows/test-other.yml
+++ b/.github/workflows/test-other.yml
@@ -33,7 +33,7 @@ jobs:
         if: inputs.os != 'amazonlinux:2023'
         with:
           distribution: 'temurin'
-          java-version: '11'
+          java-version: '21'
 
       - name: Install dependencies on Ubuntu 24.04
         if: inputs.os == 'ubuntu:24.04'
diff --git a/.github/workflows/windows-test.yml b/.github/workflows/windows-test.yml
index 917b88ff..b0cd4d4d 100644
--- a/.github/workflows/windows-test.yml
+++ b/.github/workflows/windows-test.yml
@@ -30,7 +30,7 @@ jobs:
       uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
-        java-version: '11'
+        java-version: '21'
     
     - name: Install perl
       uses: shogo82148/actions-setup-perl@v1
diff --git a/libcobj/app/build.gradle.kts b/libcobj/app/build.gradle.kts
index ad3d9da0..d0b3d4c1 100644
--- a/libcobj/app/build.gradle.kts
+++ b/libcobj/app/build.gradle.kts
@@ -24,6 +24,7 @@ tasks {
     }
     compileJava {
         options.encoding = "UTF-8"
+        options.compilerArgs.addAll(listOf("-Xlint:deprecation"))
     }
     compileTestJava {
         options.encoding = "UTF-8"
@@ -45,7 +46,7 @@ dependencies {
 
 java {
     toolchain {
-        languageVersion.set(JavaLanguageVersion.of(8))
+        languageVersion.set(JavaLanguageVersion.of(21))
     }
 }