Generated cucumber report has faulty format

Hi, I have a really strange issue when using cucumber-testng (Java, Gradle). I can run my tests successfully, but the generated report.json file has a "syntax error" in the JSON file

Basically it looks like this: 

[]  {
    "line": 1,
    "elements": [
      {....
       ....
 }
]

 So the closing "]" right in the beginning is basically the error, if you delete this character the report is in correct syntax. Does anybody have a clue why this happens? I'm using cucumber version 5.7.0. This didn't happen for me when using cucumber 4