OneToMany: Call to a member function add() on a non-object

Hi everyone, I've got a static text object and its historical revisions: StaticText 1 <→ N StaticTextHistory. So I made these relations:

StaticText.php

/**
     * @ORM\OneToMany(targetEntity="\Text\Entity\StaticTextHistory", mappedBy="staticText")
     * @var ArrayCollection
     */
    protected $history;

    public function __construct()
    {
        $this->history = new ArrayCollection();
    }

StaticTextHistory.php

/**
     * @ORM\ManyToOne(targetEntity="\Text\Entity\StaticText", inversedBy="history")
     * @ORM\JoinColumn(name="static_text_id", referencedColumnName="id", onDelete="CASCADE")
     * @var \Text\Entity\StaticText
     */
    protected $staticText;

I am trying to save StaticTextHistory object as follows:

$staticText->history->add($staticTextHistory);

And I always get error: Call to a member function add() on a non-object

When I dump $this->staticText->history, property history is an array, not an ArrayCollection.

Thanks a lot in advance.

EDIT: I have fixed this issue using getter for history property:

$staticText->getHistory()->add($staticTextHistory);

But I'm still interested what's wrong. Does it have to do anything with BaseEntity's code (starting from 240):

if ($this->$name instanceof Collection) {
                $coll = $this->$name->toArray();

                return $coll;

            }
//...

• use Doctrine\Common\Collections\ArrayCollection;