Index: debugger/command_line.ml
===================================================================
--- debugger/command_line.ml	(revision 16021)
+++ debugger/command_line.ml	(working copy)
@@ -637,10 +637,14 @@
         end
     | BA_pos1 (mdle, line, column) ->         (* break @ [MODULE] LINE [COL] *)
         let module_name = convert_module (module_of_longident mdle) in
+        let ev =  event_at_pos module_name 0 in
+        let ev_pos =
+          {Lexing.dummy_pos with pos_fname = (Events.get_pos ev).pos_fname} in
+        prerr_endline ev_pos.pos_fname;
         new_breakpoint
           (try
              let buffer =
-               try get_buffer Lexing.dummy_pos module_name with
+               try get_buffer ev_pos module_name with
                | Not_found ->
                   eprintf "No source file for %s.@." module_name;
                   raise Toplevel
Index: debugger/source.ml
===================================================================
--- debugger/source.ml	(revision 16021)
+++ debugger/source.ml	(working copy)
@@ -21,6 +21,8 @@
 (*** Conversion function. ***)

 let source_of_module pos mdle =
+  let pos_fname = pos.Lexing.pos_fname in
+  if Sys.file_exists pos_fname then pos_fname else
   let is_submodule m m' =
     let len' = String.length m' in
     try