Change RAM value of virtual machine using PowerShell

Hi,

I've created a virtual machine with initial startup memory of 512 MB. However, when I want to change it to another value, for example 1024 MB, using the Set-VM cmdlet of PowerShell, it display an error indicating that I assigned invalid startup memory amount for the virtual machine and the minimum amount that can be assigned is 8 MB. When I tried to assign 8 MB, the error still occur. 

On the other hand, when I go to the settings of the VM and change the startup RAM in Hyper-V directly, no error occur.

Thus, how can I make changes to the RAM value in PowerShell without it prompting an error?

Note: I'm setting the value in the MemoryStartupBytes parameter of the cmdlet as the VM is not using dynamic memory.

Thanks.