diff --git a/packages/ProbLog/problog.yap b/packages/ProbLog/problog.yap
index 14c184df9..c1aea1f56 100644
--- a/packages/ProbLog/problog.yap
+++ b/packages/ProbLog/problog.yap
@@ -475,6 +475,15 @@ init_global_params :-
   tmpnam(TempFolder),
   atomic_concat([TempFolder, '_problog'], TempProblogFolder),
   problog_define_flag(dir, problog_flag_validate_directory, 'directory for files', TempProblogFolder, output),
+  problog_define_flag(bdd_par_file,    problog_flag_validate_file, 'file for BDD variable parameters', example_bdd_probs, bdd, flags:working_file_handler),
+  problog_define_flag(bdd_result,      problog_flag_validate_file, 'file to store result calculated from BDD', example_bdd_res, bdd, flags:working_file_handler),
+  problog_define_flag(bdd_file,        problog_flag_validate_file, 'file for BDD script', example_bdd, bdd, flags:bdd_file_handler),
+  problog_define_flag(static_order_file,    problog_flag_validate_file, 'file for BDD static order', example_bdd_order, bdd, flags:working_file_handler),
+%%%%%%%%%%%%
+% montecarlo: recalculate current approximation after N samples
+% montecarlo: write log to this file
+%%%%%%%%%%%%
+  problog_define_flag(mc_logfile,      problog_flag_validate_file, 'logfile for montecarlo', 'log.txt', mcmc, flags:working_file_handler),
   check_existance('problogbdd').
 
 check_existance(FileName):-
@@ -488,18 +497,6 @@ check_existance(FileName):-
 % parameter initialization to be called after returning to user's directory:
 :- initialization(init_global_params).
 
-:- problog_define_flag(bdd_par_file,    problog_flag_validate_file, 'file for BDD variable parameters', example_bdd_probs, bdd).
-:- problog_define_flag(bdd_result,      problog_flag_validate_file, 'file to store result calculated from BDD', example_bdd_res, bdd).
-:- problog_define_flag(bdd_file,        problog_flag_validate_file, 'file for BDD script', example_bdd, bdd, flags:bdd_file_handler).
-:- problog_define_flag(static_order_file,    problog_flag_validate_file, 'file for BDD static order', example_bdd_order, bdd).
-
-%%%%%%%%%%%%
-% montecarlo: recalculate current approximation after N samples
-% montecarlo: write log to this file
-%%%%%%%%%%%%
-
-:- problog_define_flag(mc_logfile,      problog_flag_validate_file, 'logfile for montecarlo', 'log.txt', mcmc).
-
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % internal control flags
diff --git a/packages/ProbLog/problog/flags.yap b/packages/ProbLog/problog/flags.yap
index 53469f243..5ecd9a21a 100644
--- a/packages/ProbLog/problog/flags.yap
+++ b/packages/ProbLog/problog/flags.yap
@@ -289,6 +289,14 @@ id_stepsize_handler(stored, Value):-
 
 bdd_file_handler(message, '').
 bdd_file_handler(validating, _Value).
+bdd_file_handler(validate, Value):-
+  convert_filename_to_working_path(Value, Path),
+  catch(file_exists(Path), _, fail), file_property(Path, type(regular)), !.
+bdd_file_handler(validate, Value):-
+  convert_filename_to_working_path(Value, Path),
+  catch((not(file_exists(Path)), tell(Path)), _, fail),
+  told,
+  delete_file(Path).
 bdd_file_handler(validated, _Value).
 bdd_file_handler(stored, Value):-
   atomic_concat(Value, '_probs', ParValue),
@@ -296,6 +304,19 @@ bdd_file_handler(stored, Value):-
   atomic_concat(Value, '_res', ResValue),
   flag_set(bdd_result, ResValue).
 
+working_file_handler(message, '').
+working_file_handler(validating, _Value).
+working_file_handler(validate, Value):-
+  convert_filename_to_working_path(Value, Path),
+  catch(file_exists(Path), _, fail), file_property(Path, type(regular)), !.
+working_file_handler(validate, Value):-
+  convert_filename_to_working_path(Value, Path),
+  catch((not(file_exists(Path)), tell(Path)), _, fail),
+  told,
+  delete_file(Path).
+working_file_handler(validated, _Value).
+working_file_handler(stored, _Value).
+
 auto_handler(message, 'auto non-zero').
 auto_handler(validating, Value) :-
 	number(Value),
diff --git a/packages/ProbLog/problog/os.yap b/packages/ProbLog/problog/os.yap
index d4dfb282b..db454e2d1 100644
--- a/packages/ProbLog/problog/os.yap
+++ b/packages/ProbLog/problog/os.yap
@@ -219,7 +219,7 @@
 :- ensure_loaded(library(system)).
 
 % load our own modules
-:- ensure_loaded(flags).
+:- use_module(gflags, _, [flag_get/2]).
 
 :- dynamic [problog_path/1, problog_working_path/1].
 
@@ -228,7 +228,7 @@ set_problog_path(Path):-
 	assert(problog_path(Path)).
 
 convert_filename_to_working_path(File_Name, Path):-
-	problog_flag(dir, Dir),
+	flag_get(dir, Dir),
 	concat_path_with_filename(Dir, File_Name, Path).
 
 convert_filename_to_problog_path(File_Name, Path):-