Mapping not found in custom relation

[oligus]

Warning: array_merge(): Argument #2 is not an array in 
/Users/oli/PhpstormProjects/jad/src/Document/Resource.php on line 137

Pick up target entity and add, in this case, "support-rep" to mapping so it can be included. EntitySerializer.php:78 returns null (mapping not found)

 /**
     * @ORM\ManyToOne(targetEntity="Employees", fetch="EAGER")
     * @ORM\JoinColumn(name="SupportRepId", referencedColumnName="EmployeeId")
     */
    protected $supportRep;