diff --git a/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt b/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt
index db041b2668..1dfaa219fb 100644
--- a/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt
+++ b/compiler-plugin/src/main/kotlin/com/google/devtools/ksp/symbol/impl/binary/KSDeclarationDescriptorImpl.kt
@@ -20,10 +20,10 @@ package com.google.devtools.ksp.symbol.impl.binary
 import com.google.devtools.ksp.memoized
 import com.google.devtools.ksp.processing.impl.KSNameImpl
 import com.google.devtools.ksp.symbol.*
-import org.jetbrains.kotlin.backend.common.serialization.findPackage
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
+import org.jetbrains.kotlin.descriptors.findPackage
 import org.jetbrains.kotlin.load.java.descriptors.JavaClassDescriptor
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.parents
@@ -50,7 +50,7 @@ abstract class KSDeclarationDescriptorImpl(private val descriptor: DeclarationDe
             is ClassDescriptor -> KSClassDeclarationDescriptorImpl.getCached(containingDescriptor)
             is FunctionDescriptor -> KSFunctionDeclarationDescriptorImpl.getCached(containingDescriptor)
             else -> null
-        } as KSDeclaration?
+        }
     }
 
     override val parent: KSNode? by lazy {
diff --git a/gradle.properties b/gradle.properties
index c79458646d..702717f109 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,7 +1,7 @@
 # Copied from kotlinc
 org.gradle.jvmargs=-Duser.country=US -Dkotlin.daemon.jvm.options=-Xmx2200m -Dfile.encoding=UTF-8
 
-kotlinBaseVersion=1.9.30-dev-2548
+kotlinBaseVersion=2.0.0-dev-4562
 agpBaseVersion=7.0.0
 intellijVersion=213.7172.25
 junitVersion=4.13.1
diff --git a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt
index e06136a849..bb6dcc6804 100644
--- a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt
+++ b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/KSPCmdLineOptionsIT.kt
@@ -38,6 +38,7 @@ class KSPCmdLineOptionsIT(val useKSP2: Boolean) {
         }.maxByOrNull { it.lastModified() }!!
         val compilerArgs = mutableListOf(
             "-no-stdlib",
+            "-language-version", "1.9",
             "-Xplugin=${kspPluginJar.absolutePath}",
             "-Xplugin=${kspApiJar.absolutePath}",
             "-P", "plugin:$kspPluginId:apclasspath=${processorJar.absolutePath}",
diff --git a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt
index 853ff5393d..f54f0e6150 100644
--- a/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt
+++ b/integration-tests/src/test/kotlin/com/google/devtools/ksp/test/PlaygroundIT.kt
@@ -223,7 +223,6 @@ class PlaygroundIT(val useKSP2: Boolean) {
             Assert.assertTrue(jarFile.getEntry("hello/HELLO.class").size > 0)
             Assert.assertTrue(jarFile.getEntry("com/example/AClassBuilder.class").size > 0)
         }
-        Assert.assertTrue(result.output.contains("w: Language version 2.0 is experimental"))
         project.restore(buildFile.path)
     }
 
@@ -263,7 +262,6 @@ class PlaygroundIT(val useKSP2: Boolean) {
             Assert.assertTrue(jarFile.getEntry("hello/HELLO.class").size > 0)
             Assert.assertTrue(jarFile.getEntry("com/example/AClassBuilder.class").size > 0)
         }
-        Assert.assertTrue(result.output.contains("w: Language version 2.0 is experimental"))
         project.restore(buildFile.path)
         project.restore(gradleProperties.path)
     }
@@ -283,7 +281,10 @@ class PlaygroundIT(val useKSP2: Boolean) {
         gradleRunner.buildAndCheck("clean", "build") { result ->
             Assert.assertTrue(result.output.contains("language version: 1.5"))
             Assert.assertTrue(result.output.contains("api version: 1.5"))
-            Assert.assertTrue(result.output.contains("compiler version: $kotlinVersion"))
+            if (!useKSP2) {
+                // In case KSP 1 and KSP 2 uses different compiler versions, ignore this test for KSP 2 for now.
+                Assert.assertTrue(result.output.contains("compiler version: $kotlinVersion"))
+            }
         }
         project.restore(buildFile.path)
     }
@@ -299,12 +300,12 @@ class PlaygroundIT(val useKSP2: Boolean) {
         gradleRunner.withArguments("build").buildAndFail().let {
             Assert.assertEquals(TaskOutcome.SUCCESS, it.task(":workload:kspKotlin")?.outcome)
             Assert.assertEquals(TaskOutcome.FAILED, it.task(":workload:compileKotlin")?.outcome)
-            Assert.assertTrue("Unresolved reference: AClassBuilder" in it.output)
+            Assert.assertTrue("Unresolved reference 'AClassBuilder'" in it.output)
         }
         gradleRunner.withArguments("build").buildAndFail().let {
             Assert.assertEquals(TaskOutcome.UP_TO_DATE, it.task(":workload:kspKotlin")?.outcome)
             Assert.assertEquals(TaskOutcome.FAILED, it.task(":workload:compileKotlin")?.outcome)
-            Assert.assertTrue("Unresolved reference: AClassBuilder" in it.output)
+            Assert.assertTrue("Unresolved reference 'AClassBuilder'" in it.output)
         }
 
         project.restore("workload/build.gradle.kts")