[fpc-pascal]class methods in FPC version 1.9.0

[dean]

When porting a Kylix/Delphi project to FPC (version 1.9.0 Linux) I've 
encountered this small problem using class methods:
When I pass an object instance as parameter in class methods I have a sigsev 
like in this example

program TestFail;
uses
  SysUtils;

Type

  TMyObject = Class
  private
    FNome: string;
  published
    Property Nome: string read FNome write FNome;
  end;

  TMyTestObject = class(TObject)
  public
    class function OutputParticularClass(AObj: TObject):string;
  end;

var
  obj: TMyObject;

class function TMyTestObject.OutputParticularClass(AObj: TObject): string;
begin
  Result := AObj.ClassName;
  Writeln(Result);
end;

begin
  obj := TMyObject.Create;
  TMyTestObject.OutputParticularClass(obj);
  obj.Free;
end.

The above program compiles with no warnings in FPC, but at runtime it sigsevs.
I've run this in Kylix/Delphi and works as expected.

On the other hand I've seen that class methods work ok if the parameter passed 
are integers for example

class function TMyTestObject.OutputNumber(aNumber: integer):string; 
begin 
  Result := 'Number is ' + intToStr(aNumber); 
  Writeln(Result); 
end; 
 
begin 
  TMyTestObject.OutputNumber(12345); 
end. 
works ok in FPC

Am I doing something wrong or is a bug I've found?
Any ideas?

Ciao, Dean