diff --git a/build.gradle.kts b/build.gradle.kts
index 252cd14a..5c63759a 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -3,14 +3,14 @@ import org.gradle.api.tasks.testing.logging.TestLogEvent
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
-    kotlin("jvm") version "1.9.10" apply false
+    kotlin("jvm") version "1.8.0" apply false
     id("com.google.protobuf") version "0.9.4" apply false
     id("org.gradle.test-retry") version "1.5.5"
     id("io.github.gradle-nexus.publish-plugin") version "1.3.0"
 }
 
 group = "io.grpc"
-version = "1.3.1" // CURRENT_GRPC_KOTLIN_VERSION
+version = "1.4.0" // CURRENT_GRPC_KOTLIN_VERSION
 
 ext["grpcVersion"] = "1.57.2"
 ext["protobufVersion"] = "3.24.1"
diff --git a/compiler/build.gradle.kts b/compiler/build.gradle.kts
index 47b654a9..275a4e83 100644
--- a/compiler/build.gradle.kts
+++ b/compiler/build.gradle.kts
@@ -19,11 +19,11 @@ dependencies {
     // Misc
     implementation(kotlin("reflect"))
     implementation("com.squareup:kotlinpoet:1.14.2")
-    implementation("com.google.truth:truth:1.1.3")
+    implementation("com.google.truth:truth:1.1.5")
 
     // Testing
     testImplementation("junit:junit:4.13.2")
-    testImplementation("com.google.guava:guava:29.0-jre")
+    testImplementation("com.google.guava:guava:32.1.2-jre")
     testImplementation("com.google.jimfs:jimfs:1.3.0")
     testImplementation("com.google.protobuf:protobuf-gradle-plugin:0.9.4")
     testImplementation("com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0")
diff --git a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubject.kt b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubject.kt
index 60ca4209..eaf02581 100644
--- a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubject.kt
+++ b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubject.kt
@@ -32,12 +32,12 @@ fun assertThat(declarations: Declarations): DeclarationsSubject =
 /** A Truth subject for [Declarations]. */
 class DeclarationsSubject(
   failureMetadata: FailureMetadata,
-  private val actual: Declarations
+  private val actual: Declarations?
 ) : Subject(failureMetadata, actual) {
   fun generatesTopLevel(indentedCode: String) {
     val actualCode =
       FileSpec.builder("", "MyDeclarations.kt")
-        .apply { actual.writeOnlyTopLevel(this) }
+        .apply { actual?.writeOnlyTopLevel(this) }
         .build()
     check("topLevel").about(fileSpecs).that(actualCode).generates(indentedCode)
   }
@@ -45,7 +45,7 @@ class DeclarationsSubject(
   fun generatesEnclosed(indentedCode: String) {
     val actualCode =
       FileSpec.builder("", "MyDeclarations.kt")
-        .apply { actual.writeToEnclosingFile(this) }
+        .apply { actual?.writeToEnclosingFile(this) }
         .build()
     check("enclosed").about(fileSpecs).that(actualCode).generates(indentedCode)
   }
@@ -53,22 +53,22 @@ class DeclarationsSubject(
   fun generatesNoTopLevelMembers() {
     val actualCode =
       FileSpec.builder("", "MyDeclarations.kt")
-        .apply { actual.writeOnlyTopLevel(this) }
+        .apply { actual?.writeOnlyTopLevel(this) }
         .build()
     check("topLevel")
       .withMessage("top level declarations: %s", actualCode)
-      .that(actual.hasTopLevelDeclarations)
+      .that(actual?.hasTopLevelDeclarations)
       .isFalse()
   }
 
   fun generatesNoEnclosedMembers() {
     val actualCode =
       FileSpec.builder("", "MyDeclarations.kt")
-        .apply { actual.writeToEnclosingFile(this) }
+        .apply { actual?.writeToEnclosingFile(this) }
         .build()
     check("enclosed")
       .withMessage("enclosed declarations: %s", actualCode)
-      .that(actual.hasEnclosingScopeDeclarations)
+      .that(actual?.hasEnclosingScopeDeclarations)
       .isFalse()
   }
 }
diff --git a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FileSpecSubject.kt b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FileSpecSubject.kt
index c45f0833..af65122b 100644
--- a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FileSpecSubject.kt
+++ b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FileSpecSubject.kt
@@ -29,7 +29,7 @@ fun assertThat(fileSpec: FileSpec): FileSpecSubject = assertAbout(fileSpecs).tha
 /** A Truth subject for [FileSpec]. */
 class FileSpecSubject(
   failureMetadata: FailureMetadata,
-  private val actual: FileSpec
+  private val actual: FileSpec?
 ) : Subject(failureMetadata, actual) {
   fun generates(indentedCode: String) {
     val expectedCode = indentedCode.trimIndent()
@@ -38,6 +38,6 @@ class FileSpecSubject(
   }
 
   fun hasName(name: String) {
-    check("name").that(actual.name).isEqualTo(name)
+    check("name").that(actual?.name).isEqualTo(name)
   }
 }
diff --git a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FunSpecSubject.kt b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FunSpecSubject.kt
index 38af3c5b..9018a5c8 100644
--- a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FunSpecSubject.kt
+++ b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/FunSpecSubject.kt
@@ -29,7 +29,7 @@ fun assertThat(funSpec: FunSpec): FunSpecSubject = Truth.assertAbout(funSpecs).t
 /** A Truth subject for [FunSpec]. */
 class FunSpecSubject(
   failureMetadata: FailureMetadata,
-  private val actual: FunSpec
+  private val actual: FunSpec?
 ) : Subject(failureMetadata, actual) {
   fun generates(indentedCode: String) {
     val expectedCode = indentedCode.trimIndent()
diff --git a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/TypeSpecSubject.kt b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/TypeSpecSubject.kt
index 2d7e7a60..6988b73f 100644
--- a/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/TypeSpecSubject.kt
+++ b/compiler/src/main/java/io/grpc/kotlin/generator/protoc/testing/TypeSpecSubject.kt
@@ -29,7 +29,7 @@ fun assertThat(typeSpec: TypeSpec): TypeSpecSubject = assertAbout(typeSpecs).tha
 /** A Truth subject for [TypeSpec]. */
 class TypeSpecSubject(
   failureMetadata: FailureMetadata,
-  private val actual: TypeSpec
+  private val actual: TypeSpec?
 ) : Subject(failureMetadata, actual) {
   fun generates(indentedCode: String) {
     val expectedCode = indentedCode.trimIndent()
diff --git a/compiler/src/test/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubjectTest.kt b/compiler/src/test/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubjectTest.kt
index f87efbfa..9c830cb8 100644
--- a/compiler/src/test/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubjectTest.kt
+++ b/compiler/src/test/java/io/grpc/kotlin/generator/protoc/testing/DeclarationsSubjectTest.kt
@@ -16,7 +16,6 @@
 
 package io.grpc.kotlin.generator.protoc.testing
 
-import com.google.common.truth.ExpectFailure.SimpleSubjectBuilderCallback
 import com.google.common.truth.ExpectFailure.expectFailureAbout
 import com.squareup.kotlinpoet.INT
 import com.squareup.kotlinpoet.PropertySpec
diff --git a/examples/build.gradle.kts b/examples/build.gradle.kts
index a1421434..5a79c0a3 100644
--- a/examples/build.gradle.kts
+++ b/examples/build.gradle.kts
@@ -2,12 +2,12 @@ plugins {
     id("com.android.application") version "8.1.1" apply false
     id("com.google.protobuf") version "0.9.4" apply false
     kotlin("jvm") version "1.9.10" apply false
-    id("org.jlleitschuh.gradle.ktlint") version "11.5.1" apply false
+    id("org.jlleitschuh.gradle.ktlint") version "11.6.0" apply false
 }
 
 // todo: move to subprojects, but how?
 ext["grpcVersion"] = "1.57.2"
-ext["grpcKotlinVersion"] = "1.3.1" // CURRENT_GRPC_KOTLIN_VERSION
+ext["grpcKotlinVersion"] = "1.4.0" // CURRENT_GRPC_KOTLIN_VERSION
 ext["protobufVersion"] = "3.24.1"
 ext["coroutinesVersion"] = "1.7.3"
 
diff --git a/interop_testing/build.gradle.kts b/interop_testing/build.gradle.kts
index a4e5190a..6f362b09 100644
--- a/interop_testing/build.gradle.kts
+++ b/interop_testing/build.gradle.kts
@@ -20,7 +20,7 @@ dependencies {
 
     implementation("com.google.protobuf:protobuf-java:${rootProject.ext["protobufVersion"]}")
 
-    implementation("com.google.truth:truth:1.1.3")
+    implementation("com.google.truth:truth:1.1.5")
 
     testImplementation("org.mockito:mockito-core:4.11.0")
     testImplementation("com.squareup.okhttp:okhttp:2.7.5") {
diff --git a/stub/build.gradle.kts b/stub/build.gradle.kts
index 66ffaf03..1e4ea4d6 100644
--- a/stub/build.gradle.kts
+++ b/stub/build.gradle.kts
@@ -85,12 +85,12 @@ tasks.withType<DokkaTask>().configureEach {
             reportUndocumented.set(true)
 
             externalDocumentationLink(
-                url = URL("https://grpc.github.io/grpc-java/javadoc/")
-                //packageListUrl = "https://grpc.github.io/grpc-java/javadoc/package-list"
+                url = "https://grpc.github.io/grpc-java/javadoc/",
+                packageListUrl = "https://grpc.github.io/grpc-java/javadoc/element-list"
             )
 
             externalDocumentationLink(
-                url = URL("https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/")
+                url = "https://kotlinlang.org/api/kotlinx.coroutines/"
             )
 
             perPackageOption {