Bug(?) Private user defined functions not visible to predicates within the module

I’m using: SWI-Prolog version 8.3.9

I want the code to: make private user defined functions visible to all predicates within the module.

But what I’m getting is: ERROR: Unknown procedure: aDict:private_udf_1/2

My code looks like this:

% demo/test modules, dicts, ordinary predicates, udfs, public/private

% call tree
%	user
%		public 1
%			public 2
%			private 1
%				public 2
%				private 2

% The call tree is implemented with ordinary predicates and with user defined functions.
% Works as expected for the ordinary predicates.
% Fails on public 1 to private 1 with user defined functions.				

:- 	module(aModule,[pred_tester/0, public_pred_1/0,public_pred_2/0, 
					 udf_tester/0, public_udf_1 /2,public_udf_2 /2

%% helper

printnl(X) :- print(X),nl.

%% pred tests

pred_tester() :- 
	printnl(pred_tester():'trying user to public_pred_1()' ),
	printnl(pred_tester():'sucessful user to aModule public_pred_1()' ).

public_pred_1()  :- 
	printnl(public_pred_1():'    trying public_pred_1() to public_pred_2()' ),
	printnl(public_pred_1():'    successful public_pred_1() to public_pred_2()' ),

	printnl(public_pred_1():'    trying public_pred_1() to private_pred_1()' ),
	printnl(public_pred_1():'    successful public_pred_1() to private_pred_1()' ).

private_pred_1()  :- 
	printnl(private_pred_1():'        trying private_pred_1() to public_pred_2()' ),
	printnl(private_pred_1():'        successful private_pred_1() to public_pred_2()' ),

	printnl(private_pred_1():'        trying private_pred_1() to private_pred_2()' ),
	printnl(private_pred_1():'        successful private_pred_1() to private_pred_2()' ).
public_pred_2()   :- true.

private_pred_2()  :- true.

%% udf tests

udf_tester() :- 
	printnl(udf_tester():'trying user to public_udf_1()' ),
	aDict{}.public_udf_1() = true,
	printnl(udf_tester():'sucessful user to aModule public_udf_1()' ).

aDict{}.public_udf_1() := true  :- 
	printnl(public_udf_1():'    trying public_udf_1() to public_udf_2()' ),
	aDict{}.public_udf_2() = true,
	printnl(public_udf_1():'    successful public_udf_1() to public_udf_2()' ),

	printnl(public_udf_1():'    trying public_udf_1() to private_udf_1()' ),
	aDict{}.private_udf_1() = true,
	printnl(public_udf_1():'    successful public_udf_1() to private_udf_1()' ).
aDict{}.private_udf_1() := true  :- 
	printnl(private_udf_1():'        trying private_udf_1() to public_udf_2()' ),
	aDict{}.public_udf_2() = true,
	printnl(private_udf_1():'        successful private_udf_1() to public_udf_2()' ),

	printnl(private_udf_1():'        trying private_udf_1() to private_udf_2()' ),
	aDict{}.private_udf_2() = true,
	printnl(private_udf_1():'        successful private_udf_1() to private_udf_2()' ).
aDict{}.public_udf_2() := true  :- true.

aDict{}.private_udf_2() := true  :- true.

/* Results
?- pred_tester().
pred_tester():'trying user to public_pred_1()'
public_pred_1():'    trying public_pred_1() to public_pred_2()'
public_pred_1():'    successful public_pred_1() to public_pred_2()'
public_pred_1():'    trying public_pred_1() to private_pred_1()'
private_pred_1():'        trying private_pred_1() to public_pred_2()'
private_pred_1():'        successful private_pred_1() to public_pred_2()'
private_pred_1():'        trying private_pred_1() to private_pred_2()'
private_pred_1():'        successful private_pred_1() to private_pred_2()'
public_pred_1():'    successful public_pred_1() to private_pred_1()'
pred_tester():'sucessful user to aModule public_pred_1()'

?- udf_tester().
udf_tester():'trying user to public_udf_1()'
public_udf_1():'    trying public_udf_1() to public_udf_2()'
public_udf_1():'    successful public_udf_1() to public_udf_2()'
public_udf_1():'    trying public_udf_1() to private_udf_1()'
ERROR: Unknown procedure: aDict:private_udf_1/2
ERROR:   [16] aDict:private_udf_1(aDict{},_37846)
ERROR:   [15] eval_dict_function(private_udf_1(),aDict,aDict{},_37880) at /Applications/SWI-Prolog.app/Contents/swipl/boot/dicts.pl:85
ERROR:   [13] aModule:public_udf_1(aDict{},true) at /Users/rgb/Documents/Software Development/Computational CT/Latest/beta/module and dict test 4.pl:56
ERROR:   [12] eval_dict_function(public_udf_1(),aDict,aDict{},true) at /Applications/SWI-Prolog.app/Contents/swipl/boot/dicts.pl:85
ERROR:   [10] aModule:udf_tester at /Users/rgb/Documents/Software Development/Computational CT/Latest/beta/module and dict test 4.pl:50
ERROR:    [9] toplevel_call(user:user: ...) at /Applications/SWI-Prolog.app/Contents/swipl/boot/toplevel.pl:1113
ERROR: Note: some frames are missing due to last-call optimization.
ERROR: Re-run your program in debug mode (:- debug.) to get more detail.
   Exception: (16) aDict:private_udf_1(aDict{}, _37038) ?