diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f48598c..170adf0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java: [ 8, 11, 17, 20 ]
+        java: [ 8, 11, 17 ]
     name: Java ${{ matrix.java }}
     steps:
       - name: Checkout with submodules
diff --git a/README.md b/README.md
index 01db9d0..b7b3844 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@
  * Supports **all available JavaCard SDK versions**: 2.1.2, 2.2.1, 2.2.2, 3.0.3, 3.0.4, 3.0.5 and 3.1.0
    * Get one from [oracle.com](https://www.oracle.com/java/technologies/javacard-sdk-downloads.html) or use the [handy Github repository](https://github.com/martinpaljak/oracle_javacard_sdks)
  * **Works on all platforms** with LTS Java 1.8+: Windows, OSX, Linux.
-   * [Usable SDK-s depend on JDK version](https://github.com/martinpaljak/ant-javacard/wiki/JavaCard-SDK-and-JDK-version-compatibility); 1.8 recommended!
+   * **[Usable SDK-s depend on JDK version](https://github.com/martinpaljak/ant-javacard/wiki/JavaCard-SDK-and-JDK-version-compatibility)**; 1.8 recommended!
  * Almost **everything integrates** or works with Ant.
    * Trigger it [from Maven](https://github.com/martinpaljak/ant-javacard/wiki/How-to-use-from-Maven) or via [Gradle wrapper](https://github.com/bertrandmartel/javacard-gradle-plugin)
  * Can be easily integrated into **continuous integration** workflows.
diff --git a/src/main/java/pro/javacard/ant/JavaCard.java b/src/main/java/pro/javacard/ant/JavaCard.java
index f495142..86c2980 100644
--- a/src/main/java/pro/javacard/ant/JavaCard.java
+++ b/src/main/java/pro/javacard/ant/JavaCard.java
@@ -190,10 +190,10 @@ public void setAID(String msg) {
         }
     }
 
-    @SuppressWarnings("serial")
     public static class HelpingBuildException extends BuildException {
+        private final static long serialVersionUID = -2365126253968479314L;
         public HelpingBuildException(String msg) {
-            super(msg + "\n\nPLEASE READ https://github.com/martinpaljak/ant-javacard#syntax");
+            super(msg + "\n\nPLEASE READ https://github.com/martinpaljak/ant-javacard#readme");
         }
     }
 
@@ -557,10 +557,12 @@ private void compile() {
             // Warn in human readable way if Java not compatible with JC Kit
             // See https://github.com/martinpaljak/ant-javacard/issues/79
             int jdkver = getCurrentJDKVersion();
-            if (jckit.getVersion().isOneOf(V211, V212, V221, V222) && jdkver > 8) {
-                throw new BuildException("Use JDK 8 with JavaCard kit v2.x");
+            if (jdkver > 17) {
+                throw new HelpingBuildException("JDK 17 LTS is the latest supported JDK.");
+            } else if (jckit.getVersion().isOneOf(V211, V212, V221, V222) && jdkver > 8) {
+                throw new HelpingBuildException("Use JDK 8 with JavaCard kit v2.x");
             } else if (jdkver > 11 && !jckit.getVersion().isOneOf(V310)) {
-                throw new BuildException("Use JDK 11 with JavaCard kit " + jckit.getVersion());
+                throw new HelpingBuildException("Use JDK 11 with JavaCard kit " + jckit.getVersion());
             }
 
             j.setTarget(javaVersion);
diff --git a/tests-20.xml b/tests-20.xml
deleted file mode 120000
index 37d84c8..0000000
--- a/tests-20.xml
+++ /dev/null
@@ -1 +0,0 @@
-tests-17.xml
\ No newline at end of file