diff --git a/.gitignore b/.gitignore
index 00d9af02..676cf296 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@ syntax: glob
 !/.idea/codeStyles
 *.iml
 
+.kotlin
 .gradle
 classes
 build/
diff --git a/build-logic/src/main/kotlin/rsocketbuild.multiplatform-base.gradle.kts b/build-logic/src/main/kotlin/rsocketbuild.multiplatform-base.gradle.kts
index daa64f65..ef87cf01 100644
--- a/build-logic/src/main/kotlin/rsocketbuild.multiplatform-base.gradle.kts
+++ b/build-logic/src/main/kotlin/rsocketbuild.multiplatform-base.gradle.kts
@@ -36,6 +36,13 @@ kotlin {
         // allWarningsAsErrors.set(true)
         progressiveMode.set(true)
         freeCompilerArgs.add("-Xrender-internal-diagnostic-names")
+        optIn.addAll(
+            // TODO: drop Transport annotations
+            OptIns.TransportApi,
+            OptIns.RSocketTransportApi,
+
+            OptIns.ExperimentalSubclassOptIn
+        )
     }
 
     sourceSets.configureEach {
@@ -55,8 +62,10 @@ kotlin {
 
     targets.withType<KotlinJvmTarget>().configureEach {
         compilations.configureEach {
-            compilerOptions.configure {
-                freeCompilerArgs.add("-Xjvm-default=all")
+            compileTaskProvider.configure {
+                compilerOptions {
+                    freeCompilerArgs.add("-Xjvm-default=all")
+                }
             }
         }
     }
diff --git a/build-logic/src/main/kotlin/rsocketbuild/OptIns.kt b/build-logic/src/main/kotlin/rsocketbuild/OptIns.kt
index dc1a8493..e02f6da8 100644
--- a/build-logic/src/main/kotlin/rsocketbuild/OptIns.kt
+++ b/build-logic/src/main/kotlin/rsocketbuild/OptIns.kt
@@ -18,6 +18,7 @@ package rsocketbuild
 
 @Suppress("ConstPropertyName")
 object OptIns {
+    const val ExperimentalSubclassOptIn = "kotlin.ExperimentalSubclassOptIn"
     const val ExperimentalStdlibApi = "kotlin.ExperimentalStdlibApi"
     const val ExperimentalCoroutinesApi = "kotlinx.coroutines.ExperimentalCoroutinesApi"
     const val DelicateCoroutinesApi = "kotlinx.coroutines.DelicateCoroutinesApi"
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 1c761c83..904da916 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,5 +1,5 @@
 [versions]
-kotlin = "1.9.22"
+kotlin = "2.0.0-RC1"
 
 kotlinx-atomicfu = "0.23.2"
 kotlinx-coroutines = "1.8.0"