diff --git a/README.md b/README.md
index e2bb7ad..f121c24 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,7 @@ This codebase implements a Kotlin compiler plugin that can be used together with
 [scip-java](https://sourcegraph.github.io/scip-java) to emit
 [SCIP](https://github.com/sourcegraph/scip) indexes for Kotlin projects.
 
+
 ## Getting started
 
 This project must be used together with scip-java. Visit
@@ -12,6 +13,17 @@ This project must be used together with scip-java. Visit
 index Kotlin projects with scip-java. Note that scip-java indexes Kotlin sources
 even if you have no Java code.
 
+## Kotlin version compatibility
+
+Any given release of scip-kotlin only supports one major version of Kotlin.
+Use the table below to find the version of scip-kotlin that matches the Kotlin
+version you are using in your project.
+
+| Kotlin version | scip-kotlin version |
+|----------------|---------------------|
+| 1.8.x          | 0.3.2               |
+| 1.9.x          | 0.4.0               |
+
 ## SemanticDB support
 
 This project is implemented as a
diff --git a/build.gradle.kts b/build.gradle.kts
index 861bbed..e8d5bb2 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -4,7 +4,7 @@ import groovy.lang.Closure
 import org.gradle.jvm.toolchain.internal.CurrentJvmToolchainSpec
 
 plugins {
-    kotlin("jvm") version "1.8.21"
+    kotlin("jvm") version "1.9.22"
     id("com.github.johnrengelman.shadow") version "7.1.0"
     id("com.palantir.git-version") version "0.12.3"
     id("io.github.gradle-nexus.publish-plugin") version "1.1.0"
diff --git a/semanticdb-kotlinc/build.gradle.kts b/semanticdb-kotlinc/build.gradle.kts
index c0057a2..bae3a63 100644
--- a/semanticdb-kotlinc/build.gradle.kts
+++ b/semanticdb-kotlinc/build.gradle.kts
@@ -35,7 +35,13 @@ dependencies {
     testImplementation(kotlin("compiler-embeddable"))
     testImplementation(kotlin("test"))
     testImplementation("io.kotest", "kotest-assertions-core", "4.6.3")
-    testImplementation("com.github.tschuchortdev", "kotlin-compile-testing", "1.5.0")
+
+    // Unable to use com.github.tschuchortdev:kotlin-compile-testing until 1.9.x support is fixed
+    //   https://github.com/tschuchortdev/kotlin-compile-testing/issues/390
+    // Until then, we use the fork from https://github.com/ZacSweers/kotlin-compile-testing instead.
+    // testImplementation("com.github.tschuchortdev", "kotlin-compile-testing", "1.5.0")
+    testImplementation("dev.zacsweers.kctfork", "core", "0.4.0")
+
     testImplementation("org.junit.jupiter", "junit-jupiter-params", "5.8.1")
     testImplementation("org.jetbrains.kotlin", "kotlin-stdlib-jdk8", "1.5.0") {
         version {
diff --git a/semanticdb-kotlinc/src/main/kotlin/com/sourcegraph/semanticdb_kotlinc/SemanticdbTextDocumentBuilder.kt b/semanticdb-kotlinc/src/main/kotlin/com/sourcegraph/semanticdb_kotlinc/SemanticdbTextDocumentBuilder.kt
index 24759c8..85da22a 100644
--- a/semanticdb-kotlinc/src/main/kotlin/com/sourcegraph/semanticdb_kotlinc/SemanticdbTextDocumentBuilder.kt
+++ b/semanticdb-kotlinc/src/main/kotlin/com/sourcegraph/semanticdb_kotlinc/SemanticdbTextDocumentBuilder.kt
@@ -15,11 +15,11 @@ import org.jetbrains.kotlin.com.intellij.navigation.NavigationItem
 import org.jetbrains.kotlin.com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.KotlinLanguage
-import org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir.JsManglerDesc.fqnString
 import org.jetbrains.kotlin.psi.KtConstructor
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.KtPropertyAccessor
 import org.jetbrains.kotlin.renderer.DescriptorRenderer
+import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.getAllSuperClassifiers
 
 @ExperimentalContracts
@@ -86,7 +86,7 @@ class SemanticdbTextDocumentBuilder(
                         // first is the class itself
                         .drop(1)
                         .filter {
-                            it.fqnString(false) !in isIgnoredSuperClass
+                            it.fqNameSafe.toString() !in isIgnoredSuperClass
                         }
                         .flatMap { cache[it] }
                         .map { it.toString() }
diff --git a/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/SemanticdbSymbolsTest.kt b/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/SemanticdbSymbolsTest.kt
index 9d88e99..8d695f2 100644
--- a/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/SemanticdbSymbolsTest.kt
+++ b/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/SemanticdbSymbolsTest.kt
@@ -7,9 +7,11 @@ import com.sourcegraph.semanticdb_kotlinc.Semanticdb.SymbolOccurrence.Role
 import com.sourcegraph.semanticdb_kotlinc.test.ExpectedSymbols.SemanticdbData
 import com.sourcegraph.semanticdb_kotlinc.test.ExpectedSymbols.SymbolCacheData
 import com.tschuchort.compiletesting.SourceFile
+import org.jetbrains.kotlin.compiler.plugin.ExperimentalCompilerApi
 import kotlin.contracts.ExperimentalContracts
 import org.junit.jupiter.api.TestFactory
 
+@ExperimentalCompilerApi
 @ExperimentalContracts
 class SemanticdbSymbolsTest {
     @TestFactory
diff --git a/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/Utils.kt b/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/Utils.kt
index 44e2c48..34f2246 100644
--- a/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/Utils.kt
+++ b/semanticdb-kotlinc/src/test/kotlin/com/sourcegraph/semanticdb_kotlinc/test/Utils.kt
@@ -44,6 +44,7 @@ data class ExpectedSymbols(
 fun SourceFile.Companion.testKt(@Language("kotlin") contents: String): SourceFile =
     kotlin("Test.kt", contents)
 
+@ExperimentalCompilerApi
 @ExperimentalContracts
 fun List<ExpectedSymbols>.mapCheckExpectedSymbols(): List<DynamicTest> =
     this.flatMap { (testName, source, symbolsData, semanticdbData) ->