diff --git a/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/CompilerTest.kt b/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/CompilerTest.kt
index eed5e85..ded58fb 100644
--- a/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/CompilerTest.kt
+++ b/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/CompilerTest.kt
@@ -188,4 +188,22 @@ class CompilerTest {
     assertThat(result.systemErr).contains(
         "error: No property for required constructor parameter a")
   }
-}
\ No newline at end of file
+
+  @Test fun badGeneratedAnnotation() {
+    val call = KotlinCompilerCall(temporaryFolder.root)
+    call.inheritClasspath = true
+    call.addService(Processor::class, JsonClassCodeGenProcessor::class)
+    call.kaptArgs[JsonClassCodeGenProcessor.OPTION_GENERATED] = "javax.annotation.GeneratedBlerg"
+    call.addKt("source.kt", """
+        |import com.squareup.moshi.JsonClass
+        |
+        |@JsonClass(generateAdapter = true)
+        |data class Foo(val a: Int)
+        |""".trimMargin())
+
+    val result = call.execute()
+    assertThat(result.exitCode).isEqualTo(ExitCode.COMPILATION_ERROR)
+    assertThat(result.systemErr).contains(
+        "Invalid option value for ${JsonClassCodeGenProcessor.OPTION_GENERATED}")
+  }
+}
diff --git a/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/KotlinCompilerCall.kt b/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/KotlinCompilerCall.kt
index 3abb126..76f6d19 100644
--- a/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/KotlinCompilerCall.kt
+++ b/kotlin-codegen/compiler/src/test/java/com/squareup/moshi/KotlinCompilerCall.kt
@@ -20,11 +20,14 @@ import okio.Buffer
 import okio.Okio
 import org.jetbrains.kotlin.cli.common.CLITool
 import org.jetbrains.kotlin.cli.jvm.K2JVMCompiler
+import java.io.ByteArrayOutputStream
 import java.io.File
 import java.io.FileOutputStream
+import java.io.ObjectOutputStream
 import java.io.PrintStream
 import java.net.URLClassLoader
 import java.net.URLDecoder
+import java.util.Base64
 import java.util.zip.ZipEntry
 import java.util.zip.ZipOutputStream
 import kotlin.reflect.KClass
@@ -38,6 +41,7 @@ class KotlinCompilerCall(var scratchDir: File) {
   var inheritClasspath = false
 
   val args = mutableListOf<String>()
+  val kaptArgs = mutableMapOf<String, String>()
   val classpath = mutableListOf<String>()
   val services = LinkedHashMultimap.create<KClass<*>, KClass<*>>()
 
@@ -73,6 +77,12 @@ class KotlinCompilerCall(var scratchDir: File) {
     }
 
     fullArgs.addAll(annotationProcessorArgs())
+    if (kaptArgs.isNotEmpty()) {
+      fullArgs.apply {
+        add("-P")
+        add("plugin:org.jetbrains.kotlin.kapt3:apoptions=${encodeOptions(kaptArgs)}")
+      }
+    }
 
     val systemErrBuffer = Buffer()
     val oldSystemErr = System.err
@@ -166,4 +176,20 @@ class KotlinCompilerCall(var scratchDir: File) {
     throw IllegalStateException("no kotlin-annotation-processing-embeddable jar on classpath:\n  " +
         "${classpathFiles().joinToString(separator = "\n  ")}}")
   }
-}
\ No newline at end of file
+
+  /**
+   * Base64 encodes a mapping of annotation processor args for kapt, borrowed from
+   * https://kotlinlang.org/docs/reference/kapt.html#apjavac-options-encoding
+   */
+  private fun encodeOptions(options: Map<String, String>): String {
+    val os = ByteArrayOutputStream()
+    ObjectOutputStream(os).use { oos ->
+      oos.writeInt(options.size)
+      for ((key, value) in options.entries) {
+        oos.writeUTF(key)
+        oos.writeUTF(value)
+      }
+    }
+    return Base64.getEncoder().encodeToString(os.toByteArray())
+  }
+}