[Lazarus] RemoveDir: Error: Identifier not found

[Jürgen Hestermann]

If I hit Alt+Up on "RemoveDir" within my program I am moved to
D:\Programme\lazarus\fpc\2.6.1\source\rtl\objpas\sysutils\diskh.inc(21,10)
with the function header declaration but when doing this again
on "RemoveDir" within this file to see the implementation I get:

Error: identifier not found: RemoveDir

Is this a bug or some kind of limitation?