Weird behaviour when property "period" is in json mock data

[blackat]

Hello, I am using json-server 0.17.4 and I have setup some mock data like this one:

[
  {
    "symbol": "AAPL",
    "date": "2023-09-30",
    "period": "FY"
  }
]

and when I hit the corresponding url to test the return of mock data I get an empty array.

If I remove the property "period" everything works as expected.

Is period a reserved word in some way?