diff --git a/kotlin-native/runtime/build.gradle.kts b/kotlin-native/runtime/build.gradle.kts
index ae1ac43f791..36e801c388c 100644
--- a/kotlin-native/runtime/build.gradle.kts
+++ b/kotlin-native/runtime/build.gradle.kts
@@ -588,6 +588,9 @@ konanArtifacts {
                 "-opt-in=kotlin.native.internal.InternalForKotlinNative",
                 "-language-version",
                 "1.9",
+                "-api-version",
+                "2.0",
+                "-Xsuppress-api-version-greater-than-language-version-error",
         )
 
         commonStdlibSrcDirs.forEach { commonSrcDir(it) }
diff --git a/libraries/stdlib/build.gradle.kts b/libraries/stdlib/build.gradle.kts
index 99ab94020fd..12a31a59241 100644
--- a/libraries/stdlib/build.gradle.kts
+++ b/libraries/stdlib/build.gradle.kts
@@ -1,6 +1,7 @@
 @file:Suppress("UNUSED_VARIABLE", "NAME_SHADOWING")
 import org.gradle.jvm.tasks.Jar
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.dsl.KotlinCommonCompilerOptions
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 import org.jetbrains.kotlin.gradle.plugin.KotlinPlatformType
 import org.jetbrains.kotlin.gradle.plugin.mpp.GenerateProjectStructureMetadata
@@ -40,6 +41,12 @@ fun outgoingConfiguration(name: String, configure: Action<Configuration> = Actio
         configure(this)
     }
 
+fun KotlinCommonCompilerOptions.mainCompilationWithK1() {
+    languageVersion = KotlinVersion.KOTLIN_1_9
+    apiVersion = KotlinVersion.KOTLIN_2_0
+    freeCompilerArgs.add("-Xsuppress-api-version-greater-than-language-version-error")
+}
+
 val configurationBuiltins = resolvingConfiguration("builtins") {
     attributes.attribute(LibraryElements.LIBRARY_ELEMENTS_ATTRIBUTE, project.objects.named(LibraryElements.JAR))
 }
@@ -83,9 +90,10 @@ kotlin {
                                 diagnosticNamesArg,
                             )
                         )
+                        mainCompilationWithK1()
                         // workaround for compiling legacy MPP metadata, remove when this compilation is not needed anymore
                         // restate the list of opt-ins
-                        compilerOptions.optIn.addAll(commonOptIns)
+                        optIn.addAll(commonOptIns)
                     }
                 }
             }
@@ -122,6 +130,7 @@ kotlin {
                                 diagnosticNamesArg,
                             )
                         )
+                        mainCompilationWithK1()
                     }
                 }
                 defaultSourceSet {
@@ -147,6 +156,7 @@ kotlin {
                                 diagnosticNamesArg,
                             )
                         )
+                        mainCompilationWithK1()
                     }
                 }
             }
@@ -165,6 +175,7 @@ kotlin {
                                 diagnosticNamesArg,
                             )
                         )
+                        mainCompilationWithK1()
                     }
                 }
             }
@@ -219,15 +230,16 @@ kotlin {
         compilations {
             all {
                 kotlinOptions {
-                    freeCompilerArgs += "-Xallow-kotlin-package"
+                    freeCompilerArgs += listOf(
+                        "-Xallow-kotlin-package",
+                        "-Xexpect-actual-classes",
+                    )
                 }
             }
-            val main by getting
-            main.apply {
+            val main by getting {
                 kotlinOptions {
                     freeCompilerArgs += listOfNotNull(
                         "-Xir-module-name=kotlin",
-                        "-Xexpect-actual-classes",
                         diagnosticNamesArg,
                     )
 
@@ -235,6 +247,9 @@ kotlin {
                         allWarningsAsErrors = true
                     }
                 }
+                compileTaskProvider.configure {
+                    compilerOptions.mainCompilationWithK1()
+                }
             }
         }
     }
@@ -251,10 +266,12 @@ kotlin {
                     diagnosticNamesArg
                 )
             }
-            val main by getting
-            main.apply {
+            val main by getting {
                 kotlinOptions.freeCompilerArgs += "-Xir-module-name=kotlin"
                 kotlinOptions.allWarningsAsErrors = true
+                compileTaskProvider.configure {
+                    compilerOptions.mainCompilationWithK1()
+                }
             }
         }
     }
diff --git a/libraries/stdlib/common/build.gradle b/libraries/stdlib/common/build.gradle
index 4248a5a7d36..c438a31f209 100644
--- a/libraries/stdlib/common/build.gradle
+++ b/libraries/stdlib/common/build.gradle
@@ -37,6 +37,8 @@ compileKotlinCommon {
 
 compileKotlinCommon {
     kotlinOptions {
+        languageVersion = "1.9"
+        apiVersion = "2.0"
         freeCompilerArgs = [
                 "-module-name", project.name,
                 "-opt-in=kotlin.RequiresOptIn",
@@ -44,6 +46,7 @@ compileKotlinCommon {
                 "-opt-in=kotlin.contracts.ExperimentalContracts",
                 "-Xallow-kotlin-package",
                 "-Xexpect-actual-classes",
+                "-Xsuppress-api-version-greater-than-language-version-error",
         ]
     }
 }
diff --git a/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts b/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts
index 5c18c28bd5b..14517533257 100644
--- a/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts
+++ b/libraries/stdlib/js-ir-minimal-for-test/build.gradle.kts
@@ -148,6 +148,8 @@ kotlin {
 }
 
 tasks.withType<KotlinCompile<*>> {
+    kotlinOptions.languageVersion = "1.9"
+    kotlinOptions.apiVersion = "2.0"
     kotlinOptions.freeCompilerArgs += listOf(
         "-Xallow-kotlin-package",
         "-Xexpect-actual-classes",
@@ -156,6 +158,7 @@ tasks.withType<KotlinCompile<*>> {
         "-opt-in=kotlin.RequiresOptIn",
         "-opt-in=kotlin.ExperimentalUnsignedTypes",
         "-opt-in=kotlin.ExperimentalStdlibApi",
+        "-Xsuppress-api-version-greater-than-language-version-error",
     )
 }
 
diff --git a/libraries/stdlib/jvm-minimal-for-test/build.gradle.kts b/libraries/stdlib/jvm-minimal-for-test/build.gradle.kts
index b011e73b3c2..c0b46b0c775 100644
--- a/libraries/stdlib/jvm-minimal-for-test/build.gradle.kts
+++ b/libraries/stdlib/jvm-minimal-for-test/build.gradle.kts
@@ -55,6 +55,8 @@ tasks.compileKotlin {
         "kotlin/enums/EnumEntries.kt"
     ).map { copySources.get().destinationDir.resolve(it) }
     kotlinOptions {
+        languageVersion = "1.9"
+        apiVersion = "2.0"
         freeCompilerArgs += listOf(
             "-Xallow-kotlin-package",
             "-Xexpect-actual-classes",
@@ -62,6 +64,7 @@ tasks.compileKotlin {
             "-opt-in=kotlin.RequiresOptIn",
             "-opt-in=kotlin.contracts.ExperimentalContracts",
             "-opt-in=kotlin.ExperimentalMultiplatform",
+            "-Xsuppress-api-version-greater-than-language-version-error",
         )
         moduleName = "kotlin-stdlib"
     }
diff --git a/libraries/stdlib/test/collections/IterableTests.kt b/libraries/stdlib/test/collections/IterableTests.kt
index 1b15aecadef..cdea3d166ba 100644
--- a/libraries/stdlib/test/collections/IterableTests.kt
+++ b/libraries/stdlib/test/collections/IterableTests.kt
@@ -543,6 +543,7 @@ abstract class IterableTests<T : Iterable<String>>(val createFrom: (Array<out St
     }
 
     @Test
+    @Suppress("USELESS_CAST") // remove suppress and casts when tests are finally compiled only with K2
     fun minusAssign() {
         // lets use a mutable variable
         var result: Iterable<String> = data
diff --git a/repo/gradle-build-conventions/buildsrc-compat/src/main/kotlin/common-configuration.gradle.kts b/repo/gradle-build-conventions/buildsrc-compat/src/main/kotlin/common-configuration.gradle.kts
index 3dca48450c3..00251529573 100644
--- a/repo/gradle-build-conventions/buildsrc-compat/src/main/kotlin/common-configuration.gradle.kts
+++ b/repo/gradle-build-conventions/buildsrc-compat/src/main/kotlin/common-configuration.gradle.kts
@@ -133,10 +133,8 @@ fun Project.configureKotlinCompilationOptions() {
 
         val coreLibProjects: List<String> by rootProject.extra
         val projectsWithForced19LanguageVersion = coreLibProjects + listOf(
-            ":kotlin-stdlib-jvm-minimal-for-test",
-            ":kotlin-stdlib-js-ir-minimal-for-test",
             ":kotlin-dom-api-compat",
-        )
+        ) - listOf(":kotlin-stdlib", ":kotlin-stdlib-common")
 
         tasks.withType<org.jetbrains.kotlin.gradle.dsl.KotlinCompile<*>>().configureEach {
             kotlinOptions {