BenchmarkDotNet returning value allocates memory

I'm using BenchmarkDotNet with .netcore 3.1 to benchmark my code. I encounter a certain issue when I get memory allocation results even though no allocation is made. Here is an snapshot of what I am doing:

    [SimpleJob(RunStrategy.Monitoring, targetCount: 100)]
    [MemoryDiagnoser]
    public class Temp
    {
        public static Person[] array1 = Enumerable.Range(0, 100).Select(x => new Person(1, 2)).ToArray();

        [Benchmark]
        public Person ReturnFirstPerson()
        {
            return array1[0];
        }
    }

Person is a simple class:

   public class Person
    {
        public int A;
        public int B;

        public Person(int a, int b)
        {
            this.A = a;
            this.B = b;
        }
    }

ReturnFirstPerson method does not compute or allocate any memory but only returns the first value in the array, these are the benchmark results:

|            Method |     Mean |    Error |   StdDev | Gen 0 | Gen 1 | Gen 2 | Allocated |
|------------------ |---------:|---------:|---------:|------:|------:|------:|----------:|
| ReturnFirstPerson | 266.4 ns | 10.55 ns | 31.10 ns |     - |     - |     - |      48 B |

Can you please explain why the results are showing memory allocation?