Debugging problem Delphi 1.0


In Delphi 1.0 (and maybe also 2.0) I've met the following problem:

The only units I'm able to step into with the integrated de{*word*81}, are those residing in the
project directory. Other units on the search path are not possible to step into. Whenever setting
a breakpoint in such a unit, a message appears when running the app, telling me that the line
contains no code..

Does anyone have a remedy for this (other than keeping all source files in the project