Quoted references parsed as string instead of reference

[FoxxMD]

Since Symfony 3.0 we can no longer use @ without it being quoted to reference a relationship, but after single quoting all my references I now get errors like

Expected value of type "apiNext\Models\Merchant" for association field "apiNext\Models\Product#$merchant", got "string" instead.  

From a yaml file that looks like this

product1 (extends product):
  merchant: '@merchant1'

where it used to work perfectly unquoted