room foreignkey fail

Product.java

import android.arch.persistence.room.ColumnInfo;
import android.arch.persistence.room.Entity;
import android.arch.persistence.room.ForeignKey;
import android.arch.persistence.room.Index;
import android.arch.persistence.room.PrimaryKey;
import static android.arch.persistence.room.ForeignKey.CASCADE;

@Entity(tableName = "product_table", foreignKeys = @ForeignKey(entity = Department.class,
                                                                parentColumns = "id",
                                                                childColumns = "dept_id",
                                                                onDelete = CASCADE),
                                                                indices = @Index(value = "dept_id"))

public class Product {

    @PrimaryKey(autoGenerate = true)
    private int id;

    @ColumnInfo(name = "products")
    private String productName;

    @ColumnInfo(name = "dept_id")
    private int deptID;

    public Product(String productName, int deptID){
        this.productName = productName;
        this.deptID = deptID;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String pName) {
        this.productName = pName;
    }

    public int getDeptID() {
        return deptID;
    }

    public void setDeptID(int deptID) {
        this.deptID = deptID;
    }
}

Department.java

package com.oakware.seven.shopmate;

import android.arch.persistence.room.ColumnInfo;
import android.arch.persistence.room.Entity;
import android.arch.persistence.room.PrimaryKey;
import android.support.annotation.NonNull;

@Entity(tableName = "department_table")
public class Department {

    @PrimaryKey(autoGenerate = true)
    private int id;

    @ColumnInfo(name = "departments")
    private String deptName;

    public Department(String deptName){
        this.deptName = deptName;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getDeptName() {
        return deptName;
    }

    public void setDeptName(String deptName) {
        this.deptName = deptName;
    }
}

ProductDao.java

package com.oakware.seven.shopmate;

import android.arch.lifecycle.LiveData;
import android.arch.persistence.room.Dao;
import android.arch.persistence.room.Insert;
import android.arch.persistence.room.OnConflictStrategy;
import android.arch.persistence.room.Query;

import java.util.List;

@Dao
public interface ProductDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insert(Product product);

    @Insert
    void insertProducts(Product... products);

    @Query("DELETE FROM product_table")
    void deleteAll();

    @Query("SELECT * FROM product_table ORDER BY products asc")
    LiveData<List<Product>> getAllProducts();
}

ShopRoomDatabase.java

package com.oakware.seven.shopmate;

import android.arch.persistence.db.SupportSQLiteDatabase;
import android.arch.persistence.room.Database;
import android.arch.persistence.room.Room;
import android.arch.persistence.room.RoomDatabase;
import android.content.Context;
import android.os.AsyncTask;
import android.support.annotation.NonNull;
import android.util.Log;

@Database(entities = {Department.class, Product.class}, version = 1)
public abstract class ShopRoomDatabase extends RoomDatabase {

    public abstract DepartmentDao departmentDao();
    public abstract ProductDao productDao();

    private static ShopRoomDatabase INSTANCE;

    public static ShopRoomDatabase getDatabase(final Context context) {
        if (INSTANCE == null) {
            synchronized (ShopRoomDatabase.class) {
                if (INSTANCE == null) {
                    //create database
                    Log.i("Database", "Instance is null, creating database");
                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                            ShopRoomDatabase.class,
                            "shop_database")
                            .addCallback(sRoomDatabaseCallback)
                            .build();
                }
            }
        }
        return INSTANCE;
    }

    private static RoomDatabase.Callback sRoomDatabaseCallback =
            new RoomDatabase.Callback() {

                @Override
                public void onOpen(@NonNull SupportSQLiteDatabase db) {
                    super.onOpen(db);
                    new PopulateDbAsync(INSTANCE).execute();
                }
            };


    private static class PopulateDbAsync extends AsyncTask<Void, Void, Void> {

        private final ProductDao mProductDao;
        private final DepartmentDao mDeptDao;

        PopulateDbAsync(ShopRoomDatabase db) {
            mDeptDao = db.departmentDao();
            mProductDao = db.productDao();

        }

        @Override
        protected Void doInBackground(final Void... params) {
            mDeptDao.deleteAll();
            mProductDao.deleteAll();

            Department department = new Department("unassigned");
            mDeptDao.insert(department);
            Log.i("department name", department.getDeptName()+ " with id "+ Integer.toString(department.getId()));
            Product product = new Product("Banana", department.getId());
            Log.i("product name", product.getProductName()+ " with DeptID "+ Integer.toString(product.getDeptID()));
            mProductDao.insert(product);
            product = new Product("Milk", department.getId());
            Log.i("product name", product.getProductName()+ " with DeptID "+ Integer.toString(product.getDeptID()));
            mProductDao.insert(product);
            return null;
        }
    }
}

Error message (with some context)

I/Database: Instance is null, creating database
D/: HostConnection::get() New Host Connection established 0x9eb15840, tid 7321
I/department name: unassigned with id 0
I/product name: Banana with DeptID 0
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
                  Process: com.oakware.seven.shopmate, PID: 7321
                  java.lang.RuntimeException: An error occurred while executing doInBackground()
                      at android.os.AsyncTask$3.done(AsyncTask.java:318)
                      at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
                      at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
                      at java.util.concurrent.FutureTask.run(FutureTask.java:242)
                      at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
                      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
                      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
                      at java.lang.Thread.run(Thread.java:761)
                   Caused by: android.database.sqlite.SQLiteConstraintException: FOREIGN KEY constraint failed (code 787)
                      at android.database.sqlite.SQLiteConnection.nativeExecuteForLastInsertedRowId(Native Method)
                      at android.database.sqlite.SQLiteConnection.executeForLastInsertedRowId(SQLiteConnection.java:782)
                      at android.database.sqlite.SQLiteSession.executeForLastInsertedRowId(SQLiteSession.java:788)
                      at android.database.sqlite.SQLiteStatement.executeInsert(SQLiteStatement.java:86)
                      at android.arch.persistence.db.framework.FrameworkSQLiteStatement.executeInsert(FrameworkSQLiteStatement.java:79)
                      at android.arch.persistence.room.EntityInsertionAdapter.insert(EntityInsertionAdapter.java:64)
                      at com.oakware.seven.shopmate.ProductDao_Impl.insert(ProductDao_Impl.java:77)
                      at com.oakware.seven.shopmate.ShopRoomDatabase$PopulateDbAsync.doInBackground(ShopRoomDatabase.java:69)
                      at com.oakware.seven.shopmate.ShopRoomDatabase$PopulateDbAsync.doInBackground(ShopRoomDatabase.java:48)
                      at android.os.AsyncTask$2.call(AsyncTask.java:304)
                      at java.util.concurrent.FutureTask.run(FutureTask.java:237)
                      at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
                      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
                      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
                      at java.lang.Thread.run(Thread.java:761)