diff --git a/app/backend/build.gradle.kts b/app/backend/build.gradle.kts
index 233b3c437b76ffc05bcfca61a507d4d218583424..8c4a90f9dd0118c99d7511556a5a1a503975d089 100644
--- a/app/backend/build.gradle.kts
+++ b/app/backend/build.gradle.kts
@@ -21,7 +21,7 @@ allOpen {
 
 group = "de.fraunhofer.iem"
 version = "0.0.2-SNAPSHOT"
-java.sourceCompatibility = JavaVersion.VERSION_21
+
 configurations {
     compileOnly {
         extendsFrom(configurations.annotationProcessor.get())
@@ -56,15 +56,11 @@ dependencies {
     testRuntimeOnly(libs.h2db)
 }
 
-tasks.named("compileKotlin", org.jetbrains.kotlin.gradle.tasks.KotlinCompilationTask::class.java) {
-    compilerOptions {
-        freeCompilerArgs.add("-Xjsr305=strict")
-    }
-}
-
 kotlin {
     compilerOptions {
+        jvmToolchain(21) 
         apiVersion.set(org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_0)
+        freeCompilerArgs.add("-Xjsr305=strict")
     }
 }
 
diff --git a/kpi-calculator/adapter/build.gradle.kts b/kpi-calculator/adapter/build.gradle.kts
index aa309758015e5c0f3f21289ba6b79ea6f865075f..ec2ec29be7ada6c488fff2a7c03587d46e1e71d8 100644
--- a/kpi-calculator/adapter/build.gradle.kts
+++ b/kpi-calculator/adapter/build.gradle.kts
@@ -17,6 +17,10 @@ dependencies {
 tasks.test {
     useJUnitPlatform()
 }
+
 kotlin {
-    jvmToolchain(21)
+    compilerOptions {
+        jvmToolchain(21)
+        apiVersion.set(org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_0)
+    }
 }
diff --git a/kpi-calculator/core/build.gradle.kts b/kpi-calculator/core/build.gradle.kts
index f18ba4f7e24fdc7c3c468adc50a7f4e6232b7f86..a8f19e03094d8693f621d360fb9ef46d02a8d49f 100644
--- a/kpi-calculator/core/build.gradle.kts
+++ b/kpi-calculator/core/build.gradle.kts
@@ -16,6 +16,10 @@ dependencies {
 tasks.test {
     useJUnitPlatform()
 }
+
 kotlin {
-    jvmToolchain(21)
+    compilerOptions {
+        jvmToolchain(21)
+        apiVersion.set(org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_0)
+    }
 }
diff --git a/kpi-calculator/model/build.gradle.kts b/kpi-calculator/model/build.gradle.kts
index f18ba4f7e24fdc7c3c468adc50a7f4e6232b7f86..c8359655f2e726103a43fca8a0f8c03508647c5b 100644
--- a/kpi-calculator/model/build.gradle.kts
+++ b/kpi-calculator/model/build.gradle.kts
@@ -16,6 +16,10 @@ dependencies {
 tasks.test {
     useJUnitPlatform()
 }
+
 kotlin {
-    jvmToolchain(21)
-}
+    compilerOptions {
+        jvmToolchain(21)
+        apiVersion.set(org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_0)
+    }
+}
\ No newline at end of file