diff --git a/waltid-libraries/auth/waltid-ktor-authnz/build.gradle.kts b/waltid-libraries/auth/waltid-ktor-authnz/build.gradle.kts
index 398122291..9e2460f11 100644
--- a/waltid-libraries/auth/waltid-ktor-authnz/build.gradle.kts
+++ b/waltid-libraries/auth/waltid-ktor-authnz/build.gradle.kts
@@ -102,6 +102,10 @@ dependencies {
     testImplementation("org.jetbrains.kotlin:kotlin-test-junit")
 }
 
+kotlin {
+    jvmToolchain(21)
+}
+
 publishing {
     publications {
         create<MavenPublication>("mavenJava") {