Invalid "Type size mismatch, possible loss of data" for for-in loop when compiling for x86_64

Summary

Consider the following program:

program test;

procedure foo;
var
  i: integer;
  a: array of integer;
begin
  a := NIL;
  for i in a do
  begin
  end;
end;

begin
  foo;
end.

Everything is fine when I compile it with fpc -vh -CO test.pas. But once I add -Px86_64, it emits a Type size mismatch, possible loss of data / range check error hint for for i in a do:

fpc -vh -CO -Px86_64 test.pas
Hint: Start of reading config file C:\FPC\3.2.2\bin\i386-Win32\fpc.cfg
Hint: End of reading config file C:\FPC\3.2.2\bin\i386-Win32\fpc.cfg
Free Pascal Compiler version 3.2.2 [2021/05/15] for x86_64
Copyright (c) 1993-2021 by Florian Klaempfl and others
Target OS: Win64 for x64
Compiling test.pas
test.pas(9,7) Hint: Type size mismatch, possible loss of data / range check error

You can also replace integer by string, and the result will still be the same.

System Information

• Operating system: Windows 7
• Processor architecture: x86-64
• Compiler version: 3.2.2
• Device: Computer