Why does the error "[ksp] java.lang.IllegalStateException: unexpected jvm signature V" occur when using Room with KSP and how can I solve it?

I am programming a small Counter app where the count should be stored in a Room database. I am using Kotlin, Jetpack Compose and Room Database with KSP. When I try to run the app the following error occurs: [ksp] java.lang.IllegalStateException: unexpected jvm signature V. When I comment out the code from CounterDatabase.kt the error disappear. Why does it occur and how do I solve it?

My files are:

build.gradle (Project)

plugins {
    alias(libs.plugins.android.application) apply false
    alias(libs.plugins.kotlin.compose) apply false

    // Room
    id("com.google.devtools.ksp") version "2.3.4" apply false
}

build.gradle (Module)

plugins {
    alias(libs.plugins.android.application)
    alias(libs.plugins.kotlin.compose)
    id("com.google.devtools.ksp")
}

android {
    namespace = "com.example.counter"
    compileSdk {
        version = release(36) {
            minorApiLevel = 1
        }
    }

    defaultConfig {
        applicationId = "com.example.counter"
        minSdk = 24
        targetSdk = 36
        versionCode = 1
        versionName = "1.0"

        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            isMinifyEnabled = false
            proguardFiles(
                getDefaultProguardFile("proguard-android-optimize.txt"),
                "proguard-rules.pro"
            )
        }
    }
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_11
        targetCompatibility = JavaVersion.VERSION_11
    }
    buildFeatures {
        compose = true
    }
}

dependencies {

    // Room
    implementation(libs.androidx.room.runtime)
    ksp(libs.androidx.room.compiler)

    implementation(libs.androidx.core.ktx)
    implementation(libs.androidx.lifecycle.runtime.ktx)
    implementation(libs.androidx.activity.compose)
    implementation(platform(libs.androidx.compose.bom))
    implementation(libs.androidx.compose.ui)
    implementation(libs.androidx.compose.ui.graphics)
    implementation(libs.androidx.compose.ui.tooling.preview)
    implementation(libs.androidx.compose.material3)
    implementation(libs.androidx.lifecycle.viewmodel.compose)
    testImplementation(libs.junit)
    androidTestImplementation(libs.androidx.junit)
    androidTestImplementation(libs.androidx.espresso.core)
    androidTestImplementation(platform(libs.androidx.compose.bom))
    androidTestImplementation(libs.androidx.compose.ui.test.junit4)
    debugImplementation(libs.androidx.compose.ui.tooling)
    debugImplementation(libs.androidx.compose.ui.test.manifest)
}

libs.versions.toml

[versions]
agp = "9.2.0"
coreKtx = "1.10.1"
junit = "4.13.2"
junitVersion = "1.1.5"
espressoCore = "3.5.1"
lifecycleRuntimeKtx = "2.6.1"
activityCompose = "1.8.0"
kotlin = "2.2.10"
composeBom = "2026.02.01"
lifecycleViewmodelCompose = "2.10.0"
roomCompiler = "2.5.0"
roomRuntime = "2.8.4"
roomCompilerVersion = "2.8.4"

[libraries]
androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
androidx-lifecycle-viewmodel-compose = { module = "androidx.lifecycle:lifecycle-viewmodel-compose", version.ref = "lifecycleViewmodelCompose" }

androidx-room-compiler = { module = "androidx.room:room-compiler", version.ref = "roomCompiler" }
androidx-room-runtime = { module = "androidx.room:room-runtime", version.ref = "roomRuntime" }

junit = { group = "junit", name = "junit", version.ref = "junit" }
androidx-junit = { group = "androidx.test.ext", name = "junit", version.ref = "junitVersion" }
androidx-espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version.ref = "espressoCore" }
androidx-lifecycle-runtime-ktx = { group = "androidx.lifecycle", name = "lifecycle-runtime-ktx", version.ref = "lifecycleRuntimeKtx" }
androidx-activity-compose = { group = "androidx.activity", name = "activity-compose", version.ref = "activityCompose" }
androidx-compose-bom = { group = "androidx.compose", name = "compose-bom", version.ref = "composeBom" }
androidx-compose-ui = { group = "androidx.compose.ui", name = "ui" }
androidx-compose-ui-graphics = { group = "androidx.compose.ui", name = "ui-graphics" }
androidx-compose-ui-tooling = { group = "androidx.compose.ui", name = "ui-tooling" }
androidx-compose-ui-tooling-preview = { group = "androidx.compose.ui", name = "ui-tooling-preview" }
androidx-compose-ui-test-manifest = { group = "androidx.compose.ui", name = "ui-test-manifest" }
androidx-compose-ui-test-junit4 = { group = "androidx.compose.ui", name = "ui-test-junit4" }
androidx-compose-material3 = { group = "androidx.compose.material3", name = "material3" }
room-compiler = { group = "androidx.room", name = "room-compiler", version.ref = "roomCompilerVersion" }

[plugins]
android-application = { id = "com.android.application", version.ref = "agp" }
kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }

CounterDatabase.kt

In this file I do also receive the following two errors:

  • Function "counterDataAccessObject" is never used

  • Function "getDatabase" is never used

package com.example.counter.counter.database

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase

@Database(
    entities = [CounterEntity::class],
    version = 1
)
abstract class CounterDatabase : RoomDatabase() {
    abstract fun counterDataAccessObject() : CounterDataAccessObject

    companion object {
        @Volatile
        private var INSTANCE: CounterDatabase? = null

        fun getDatabase(context: Context): CounterDatabase {
            return INSTANCE ?: synchronized(this) {
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    CounterDatabase::class.java,
                    "CounterDatabase"
                ).build()
                INSTANCE = instance
                instance
            }
        }
    }
}

Dao file

package com.example.counter.counter.database

import androidx.room.Dao
import androidx.room.Query

@Dao
interface CounterDataAccessObject {

    @Query("SELECT count FROM CounterEntity WHERE id = :id")
    suspend fun getCount(id: Int): Int?

    @Query("UPDATE CounterEntity SET count = count + 1 WHERE id = :id")
    suspend fun incrementCount(id: Int)

    @Query("UPDATE CounterEntity SET count = count - 1 WHERE id = :id")
    suspend fun decrementCount(id: Int)

}

Entity file

package com.example.counter.counter.database

import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity
data class CounterEntity(
    @PrimaryKey(autoGenerate = true) val id: Int = 0,
    val count: Int)
1
May 2 at 2:03 PM
User AvatarBenedikt Schlüter
#android#kotlin#android-room

Accepted Answer

You are mixing Room artifacts of different versions. That is bound to result in incompatibilities.

In your version catalog, you have these three versions defined:

roomCompiler = "2.5.0"
roomRuntime = "2.8.4"
roomCompilerVersion = "2.8.4"

Replace them with only one version definition:

room = "2.8.4"

Update the libraries androidx-room-compiler and androidx-room-runtime to use that instead.

You also have the redundant library room-compiler defined in the version catalog. Remove it, it isn't even used anywhere.

After a Gradle sync, your app should be able to be built again.

User Avatartyg
May 2 at 10:58 PM
2