diff --git a/lib/kotlin/build.gradle.kts b/lib/kotlin/build.gradle.kts
index 90b9e80..06b73f2 100644
--- a/lib/kotlin/build.gradle.kts
+++ b/lib/kotlin/build.gradle.kts
@@ -36,7 +36,7 @@
 
 kotlin {
     jvmToolchain {
-        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(8))
+        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(11))
     }
 }
 
diff --git a/lib/kotlin/cross-test-client/build.gradle.kts b/lib/kotlin/cross-test-client/build.gradle.kts
index ff48eed..579d01e 100644
--- a/lib/kotlin/cross-test-client/build.gradle.kts
+++ b/lib/kotlin/cross-test-client/build.gradle.kts
@@ -52,7 +52,7 @@
 
 kotlin {
     jvmToolchain {
-        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(8))
+        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(11))
     }
 }
 
diff --git a/lib/kotlin/cross-test-server/build.gradle.kts b/lib/kotlin/cross-test-server/build.gradle.kts
index eda1ebd..4f6e12d 100644
--- a/lib/kotlin/cross-test-server/build.gradle.kts
+++ b/lib/kotlin/cross-test-server/build.gradle.kts
@@ -50,7 +50,7 @@
 
 kotlin {
     jvmToolchain {
-        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(8))
+        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(11))
     }
 }