diff --git a/build.gradle.kts b/build.gradle.kts
index 75ca30bc..c76e253e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -3,6 +3,8 @@ import com.adarshr.gradle.testlogger.theme.ThemeType.MOCHA_PARALLEL
 import com.github.benmanes.gradle.versions.updates.DependencyUpdatesTask
 import io.codearte.gradle.nexus.NexusStagingExtension
 import org.gradle.api.JavaVersion.VERSION_17
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17
+import org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_0
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 import org.jmailen.gradle.kotlinter.KotlinterExtension
 import kotlin.text.RegexOption.IGNORE_CASE
@@ -10,11 +12,11 @@ import kotlin.text.RegexOption.IGNORE_CASE
 plugins {
   kotlin("jvm") apply false
   id("io.codearte.nexus-staging") version "0.30.0"
-  id("org.jmailen.kotlinter") version "4.4.0" apply false
+  id("org.jmailen.kotlinter") version "4.4.1" apply false
   id("com.adarshr.test-logger") version "4.0.0" apply false
   id("com.github.ben-manes.versions") version "0.51.0"
   id("org.jetbrains.dokka")
-  id("org.jetbrains.kotlinx.kover") version "0.8.1"
+  id("org.jetbrains.kotlinx.kover") version "0.8.3"
 }
 
 repositories {
@@ -53,9 +55,9 @@ subprojects {
       }
 
       tasks.withType<KotlinCompile> {
-        kotlinOptions {
-          jvmTarget = VERSION_17.toString()
-          languageVersion = "1.9"
+        compilerOptions {
+          jvmTarget.set(JVM_17)
+          languageVersion.set(KOTLIN_2_0)
           javaParameters = true
           freeCompilerArgs = listOf("-Xjvm-default=all")
           allWarningsAsErrors = true
diff --git a/gradle.properties b/gradle.properties
index 8716819b..a2e0dcf4 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -5,12 +5,12 @@ org.gradle.jvmargs=-XX:MaxMetaspaceSize=1024m
 versions.arrow=1.2.4
 versions.failgood=0.9.1
 versions.filepeek=0.1.3
-versions.jackson=2.17.1
-versions.junit=5.10.2
-versions.kotlin=1.9.20
+versions.jackson=2.17.2
+versions.junit=5.10.3
+versions.kotlin=2.0.10
 versions.kotlinx-coroutines=1.8.1
 versions.minutest=1.13.0
-versions.mockk=1.13.11
-versions.protobuf=4.27.1
+versions.mockk=1.13.12
+versions.protobuf=4.27.3
 versions.opentest4j=1.3.0
-versions.spring-boot=3.3.1
+versions.spring-boot=3.3.2
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 7f93135c..e6441136 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index a4413138..09523c0e 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.8-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
diff --git a/gradlew b/gradlew
index 1aa94a42..b740cf13 100755
--- a/gradlew
+++ b/gradlew
@@ -55,7 +55,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
diff --git a/gradlew.bat b/gradlew.bat
index 93e3f59f..25da30db 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -43,11 +43,11 @@ set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
 if %ERRORLEVEL% equ 0 goto execute
 
-echo.
-echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
 goto fail
 
@@ -57,11 +57,11 @@ set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
 if exist "%JAVA_EXE%" goto execute
 
-echo.
-echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
 goto fail
 
diff --git a/strikt-core/src/test/kotlin/strikt/Chained.kt b/strikt-core/src/test/kotlin/strikt/Chained.kt
index d4b5441a..e2732cbe 100644
--- a/strikt-core/src/test/kotlin/strikt/Chained.kt
+++ b/strikt-core/src/test/kotlin/strikt/Chained.kt
@@ -75,6 +75,7 @@ internal class Chained {
       .isEqualTo(expected)
   }
 
+  @Suppress("RedundantNullableReturnType")
   @Test
   fun `can connect a block to a chain with and`() {
     val error =
diff --git a/strikt-core/src/test/kotlin/strikt/docs/Homepage.kt b/strikt-core/src/test/kotlin/strikt/docs/Homepage.kt
index cd24cb28..7af1bcf9 100644
--- a/strikt-core/src/test/kotlin/strikt/docs/Homepage.kt
+++ b/strikt-core/src/test/kotlin/strikt/docs/Homepage.kt
@@ -56,7 +56,7 @@ internal class Homepage {
   @Test
   fun `homepage four`() {
     // START homepage_four
-    val subject = Deity.values().map { it.toString() }
+    val subject = Deity.entries.map { it.toString() }
     expectThat(subject)
       .isNotEmpty()
       .any { startsWith("E") }
@@ -104,7 +104,7 @@ internal class Homepage {
     // END homepage_seven
   }
 
-  @Suppress("ktlint:standard:no-multi-spaces")
+  @Suppress("ktlint:standard:no-multi-spaces", "RedundantNullableReturnType")
   @Test
   fun `homepage eight`() {
     // START homepage_eight
diff --git a/strikt-protobuf/strikt-protobuf.gradle.kts b/strikt-protobuf/strikt-protobuf.gradle.kts
index bd9f31b1..5f681c73 100644
--- a/strikt-protobuf/strikt-protobuf.gradle.kts
+++ b/strikt-protobuf/strikt-protobuf.gradle.kts
@@ -1,7 +1,6 @@
 @file:Suppress("KDocMissingDocumentation")
 
 import org.jetbrains.dokka.gradle.DokkaTaskPartial
-import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import java.net.URL
 
 plugins {
@@ -41,18 +40,11 @@ protobuf {
   }
 }
 
-// This seems to be necessary just to get IntelliJ to notice the proto sources.
-// It works fine from the terminal without this. Also IntelliJ picks up main
-// protos just fine.
-
-val SourceSet.kotlin
-  get() = withConvention(KotlinSourceSet::class) { kotlin }
-
 sourceSets {
   getByName("test") {
     kotlin.srcDirs(
       "src/test/kotlin",
-      "$buildDir/generated/source/proto/test/java"
+      "$buildFile/generated/source/proto/test/java"
     )
   }
 }