diff --git a/build.gradle.kts b/build.gradle.kts
index 17077fb6..9f951c63 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,9 +1,11 @@
 import io.gitlab.arturbosch.detekt.Detekt
-import org.gradle.jvm.tasks.Jar
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat.FULL
+import org.gradle.jvm.tasks.Jar
+import org.jetbrains.kotlin.gradle.ExperimentalKotlinGradlePluginApi
+import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 
 plugins {
-    kotlin("multiplatform") version "1.8.22"
+    kotlin("multiplatform") version "1.9.21"
     id("org.jetbrains.dokka") version "1.8.20"
     `maven-publish`
     id("io.github.gradle-nexus.publish-plugin") version "1.3.0"
@@ -40,17 +42,25 @@ apply(plugin = "io.github.gradle-nexus.publish-plugin")
 
 kotlin {
     explicitApi()
+
+    @OptIn(ExperimentalKotlinGradlePluginApi::class)
+    compilerOptions {
+        // kotlin compiler compatibility options
+        apiVersion.set(KotlinVersion.KOTLIN_1_9)
+        languageVersion.set(KotlinVersion.KOTLIN_1_9)
+
+        freeCompilerArgs.add("-Xexpect-actual-classes")
+    }
+
     jvm {
         compilations.all {
             // kotlin compiler compatibility options
             kotlinOptions {
-                apiVersion = "1.4"
-                languageVersion = "1.4"
                 jvmTarget = "1.8"
             }
         }
     }
-    js(BOTH) {
+    js {
         browser {
             testTask {
                 useKarma {
diff --git a/gradle.properties b/gradle.properties
index a26c047d..b46c029c 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -5,3 +5,4 @@ systemProp.org.gradle.internal.publish.checksums.insecure=true
 org.gradle.jvmargs=-Xmx2048m
 # see https://kotlinlang.org/docs/whatsnew18.html#sourcedirectories
 kotlin.mpp.androidSourceSetLayoutVersion=2
+kotlin.mpp.applyDefaultHierarchyTemplate=false
diff --git a/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/DarwinKLogger.kt b/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/DarwinKLogger.kt
index 59e89aaa..24a5bb78 100644
--- a/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/DarwinKLogger.kt
+++ b/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/DarwinKLogger.kt
@@ -1,5 +1,8 @@
+@file:OptIn(ExperimentalForeignApi::class)
+
 package io.github.oshai.kotlinlogging
 
+import kotlinx.cinterop.ExperimentalForeignApi
 import kotlinx.cinterop.ptr
 import platform.darwin.OS_LOG_TYPE_DEBUG
 import platform.darwin.OS_LOG_TYPE_DEFAULT
diff --git a/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt b/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt
index d9b2c927..0b32ce6d 100644
--- a/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt
+++ b/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt
@@ -1,6 +1,6 @@
 package io.github.oshai.kotlinlogging
 
-import kotlin.native.concurrent.AtomicReference
+import kotlin.concurrent.AtomicReference
 
 public object KotlinLoggingConfiguration {
   public var subsystem: AtomicReference<String?> = AtomicReference(null)
diff --git a/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/internal/KLoggerFactory.kt b/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/internal/KLoggerFactory.kt
index 41592817..882dae95 100644
--- a/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/internal/KLoggerFactory.kt
+++ b/src/darwinMain/kotlin/io/github/oshai/kotlinlogging/internal/KLoggerFactory.kt
@@ -3,7 +3,7 @@ package io.github.oshai.kotlinlogging.internal
 import io.github.oshai.kotlinlogging.DarwinKLogger
 import io.github.oshai.kotlinlogging.KLogger
 import io.github.oshai.kotlinlogging.KotlinLoggingConfiguration
-import kotlin.native.concurrent.AtomicReference
+import kotlin.concurrent.AtomicReference
 import platform.darwin.OS_LOG_DEFAULT
 import platform.darwin.os_log_create
 
diff --git a/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/ConsoleOutputAppender.kt b/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/ConsoleOutputAppender.kt
index a51ed3c0..92625262 100644
--- a/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/ConsoleOutputAppender.kt
+++ b/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/ConsoleOutputAppender.kt
@@ -1,5 +1,8 @@
+@file:OptIn(ExperimentalForeignApi::class)
+
 package io.github.oshai.kotlinlogging
 
+import kotlinx.cinterop.ExperimentalForeignApi
 import platform.posix.fprintf
 import platform.posix.stderr
 
diff --git a/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt b/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt
index 9ca99631..646980ff 100644
--- a/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt
+++ b/src/nativeMain/kotlin/io/github/oshai/kotlinlogging/KotlinLoggingConfiguration.kt
@@ -1,6 +1,6 @@
 package io.github.oshai.kotlinlogging
 
-import kotlin.native.concurrent.AtomicReference
+import kotlin.concurrent.AtomicReference
 
 public expect val DefaultAppender: Appender