Symfony Doctrine Insert: cannot insert into column "id"

I'm modeling a vending machine where I got 3 Entities (Milk, Sugar, Coffee) and one table that lists all my coffee machines.

Now I want to insert a new value for the amount of milk left. The coffee machines are foreign keys in the resources tables.

However, I get this error, which does not seem to make sense, as I am just setting a foreign key field:

An exception occurred while executing a query: SQLSTATE[428C9]: <<Unknown error>>: 7 ERROR: cannot insert into column "id" DETAIL: Column "id" is an identity column defined as GENERATED ALWAYS. HINT: Use OVERRIDING SYSTEM VALUE to override. 

Here are the tables (Postgres) (only coffee listed - milk and sugar have the same architecture):

create table coffee ( id integer not null generated always as identity primary key, request_id bigint, logdate timestamp(0) without time zone not null, vmc_no integer, amount integer not null, constraint fk_request foreign key(request_id) references energyomat.request(id), constraint fk_vmc_company foreign key(vmc_no) references energyomat.vmc_company(vmc_no) ); create table vmc_company ( vmc_no integer not null unique primary key, register_date timestamp(0) without time zone not null ); 

I've set the primitive fields and got the Entity of VmcCompany and set it as the foreign value (setVmcNo).

public function updateResources($vmcNo, $milkAmount, $sugarAmount, $coffeeAmount) { $milk = new Milk(); $sugar = new Sugar(); $coffee = new Coffee(); if($milkAmount != null) { $milk->setAmount($milkAmount); $milk->setLogdate(new \DateTime()); $vmc = $this->doctrine->getRepository(VmcCompany::class)->find($vmcNo); $milk->setVmcNo($vmc); $manager = $this->doctrine->getManager(); $manager->persist($milk); } if($sugarAmount != null) { $sugar->setAmount($sugarAmount); $sugar->setLogdate(new \DateTime()); $vmc = $this->doctrine->getRepository(VmcCompany::class)->find($vmcNo); $sugar->setVmcNo($vmc); $manager = $this->doctrine->getManager(); $manager->persist($sugar); } if($coffeeAmount != null) { $coffee->setAmount($coffeeAmount); $coffee->setLogdate(new \DateTime()); $vmc = $this->doctrine->getRepository(VmcCompany::class)->find($vmcNo); $coffee->setVmcNo($vmc); $manager = $this->doctrine->getManager(); $manager->persist($coffee); } $manager->flush(); } 

Here are the Entity classes: Coffee:

<?php namespace App\Entity; use Doctrine\ORM\Mapping as ORM; /** * Coffee * * @ORM\Table(name="coffee", indexes={@ORM\Index(name="IDX_538529B3427EB8A5", columns={"request_id"}), @ORM\Index(name="IDX_538529B3651BF703", columns={"vmc_no"})}) * @ORM\Entity */ class Coffee { /** * @var int * * @ORM\Column(name="id", type="integer", nullable=false) * @ORM\Id * @ORM\GeneratedValue(strategy="SEQUENCE") * @ORM\SequenceGenerator(sequenceName="coffee_id_seq", allocationSize=1, initialValue=1) */ private $id; /** * @var \DateTime * * @ORM\Column(name="logdate", type="datetime", nullable=false) */ private $logdate; /** * @var int * * @ORM\Column(name="amount", type="integer", nullable=false) */ private $amount; /** * @var \Request * * @ORM\ManyToOne(targetEntity="Request") * @ORM\JoinColumns({ * @ORM\JoinColumn(name="request_id", referencedColumnName="id") * }) */ private $request; /** * @var \VmcCompany * * @ORM\ManyToOne(targetEntity="VmcCompany") * @ORM\JoinColumns({ * @ORM\JoinColumn(name="vmc_no", referencedColumnName="vmc_no") * }) */ private $vmcNo; public function getId(): ?int { return $this->id; } public function getLogdate(): ?\DateTimeInterface { return $this->logdate; } public function setLogdate(\DateTimeInterface $logdate): self { $this->logdate = $logdate; return $this; } public function getAmount(): ?int { return $this->amount; } public function setAmount(int $amount): self { $this->amount = $amount; return $this; } public function getRequest(): ?Request { return $this->request; } public function setRequest(?Request $request): self { $this->request = $request; return $this; } public function getVmcNo(): ?VmcCompany { return $this->vmcNo; } public function setVmcNo(?VmcCompany $vmcNo): self { $this->vmcNo = $vmcNo; return $this; } } 

VmcCompany:

<?php namespace App\Entity; use Doctrine\ORM\Mapping as ORM; /** * VmcCompany * * @ORM\Table(name="vmc_company") * @ORM\Entity */ class VmcCompany { /** * @var int * * @ORM\Column(name="vmc_no", type="integer", nullable=false) * @ORM\Id * @ORM\GeneratedValue(strategy="SEQUENCE") * @ORM\SequenceGenerator(sequenceName="vmc_company_vmc_no_seq", allocationSize=1, initialValue=1) */ private $vmcNo; /** * @var \DateTime * * @ORM\Column(name="register_date", type="datetime", nullable=false) */ private $registerDate; public function getVmcNo(): ?int { return $this->vmcNo; } public function getRegisterDate(): ?\DateTimeInterface { return $this->registerDate; } public function setRegisterDate(\DateTimeInterface $registerDate): self { $this->registerDate = $registerDate; return $this; } } 

I'm new to Symfony / Doctrine and so I guess I'm overseeing something, but just cannot find out what it is. Thanks for your help in advance.