diff --git a/build.gradle.kts b/build.gradle.kts
index 1842e03..8d8df9b 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -21,6 +21,23 @@ plugins {
     alias(libs.plugins.vanniktech.mavenPublish) apply false
 }
 
+// Some JVM dependencies are published as Java 21 bytecode. Keep the library's
+// Java 17 compilation target, but use a compatible runtime for its JVM tests.
+project(":lynglib") {
+    afterEvaluate {
+        val toolchains = extensions.getByType<org.gradle.jvm.toolchain.JavaToolchainService>()
+        tasks.withType<Test>().configureEach {
+            javaLauncher.set(toolchains.launcherFor {
+                languageVersion.set(JavaLanguageVersion.of(21))
+            })
+            // An explicit jvmTest invocation should execute the suite rather than
+            // silently reusing the previous test task outputs or build-cache entry.
+            outputs.upToDateWhen { false }
+            outputs.cacheIf { false }
+        }
+    }
+}
+
 // Convenience alias to run the IntelliJ IDE with the Lyng plugin from the project root.
 // Usage: ./gradlew runIde
 // It simply delegates to :lyng-idea:runIde provided by the Gradle IntelliJ Plugin.
diff --git a/gradle.properties b/gradle.properties
index c4d6800..e0fc8ad 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -16,7 +16,8 @@
 #
 
 #Gradle
-org.gradle.jvmargs=-Xmx4096M -Dfile.encoding=UTF-8 -Dkotlin.daemon.jvm.options\="-Xmx2048M"
+org.gradle.jvmargs=-Xmx4096M -Dfile.encoding=UTF-8 -Dkotlin.daemon.jvm.options\="-Xmx2048M" --add-opens=java.base/java.lang=ALL-UNNAMED
+org.gradle.java.home=/usr/lib/jvm/java-17-openjdk-amd64
 org.gradle.caching=true
 org.gradle.configuration-cache=true
 #Kotlin
diff --git a/lynglib/build.gradle.kts b/lynglib/build.gradle.kts
index ba1a659..505de24 100644
--- a/lynglib/build.gradle.kts
+++ b/lynglib/build.gradle.kts
@@ -47,7 +47,11 @@ buildkonfig {
 
 kotlin {
     jvmToolchain(17)
-    jvm()
+    jvm {
+        compilerOptions {
+            jvmTarget.set(JvmTarget.JVM_17)
+        }
+    }
     androidTarget {
         publishLibraryVariants("release")
         @OptIn(ExperimentalKotlinGradlePluginApi::class)
@@ -297,8 +301,8 @@ android {
         minSdk = libs.versions.android.minSdk.get().toInt()
     }
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_11
-        targetCompatibility = JavaVersion.VERSION_11
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
     }
 }
 dependencies {