diff --git a/C/init.c b/C/init.c
index be6413108..9c9ae231e 100644
--- a/C/init.c
+++ b/C/init.c
@@ -354,6 +354,7 @@ static Opdef    Ops[] = {
   {"dynamic", fx, 1150},
   {"thread_local", fx, 1150},
   {"initialization", fx, 1150},
+  {"volatile", fx, 1150},
   {"mode", fx, 1150},
   {"public", fx, 1150},
   {"multifile", fx, 1150},
diff --git a/library/dialect/swi.yap b/library/dialect/swi.yap
index 8a18400ec..d4769b29a 100755
--- a/library/dialect/swi.yap
+++ b/library/dialect/swi.yap
@@ -203,21 +203,6 @@ predmerge(<, P, H1, H2, T1, T2, [H1|R]) :-
 % maybe a good idea to eventually support this in YAP.
 % but for now just ignore it.
 %
-:- meta_predicate prolog:volatile(:).
-
-:- op(1150, fx, 'volatile').
-
-prolog:volatile(P) :- var(P),
-	throw(error(instantiation_error,volatile(P))).
-prolog:volatile(M:P) :-
-	do_volatile(P,M).
-prolog:volatile((G1,G2)) :-
-	prolog:volatile(G1),
-	prolog:volatile(G2).
-prolog:volatile(P) :-
-	prolog_load_context(module, M),
-	do_volatile(P,M).
-
 prolog:load_foreign_library(P,Command) :-
 	absolute_file_name(P,[file_type(executable),solutions(first),file_errors(fail)],Lib),
 	load_foreign_files([Lib],[],Command).
@@ -225,8 +210,6 @@ prolog:load_foreign_library(P,Command) :-
 prolog:load_foreign_library(P) :-
 	prolog:load_foreign_library(P,install).
 
-do_volatile(P,M) :- dynamic(M:P).
-
 :- use_module(library(lists)).
 
 prolog:term_to_atom(Term,Atom) :-
diff --git a/pl/threads.yap b/pl/threads.yap
index 91fb22904..a44d039fc 100644
--- a/pl/threads.yap
+++ b/pl/threads.yap
@@ -21,7 +21,22 @@
 	thread_create(:),
 	thread_at_exit(:),
 	thread_signal(+,:),
-	with_mutex(+,:).
+	with_mutex(+,:),
+	volatile(:).
+
+volatile(P) :- var(P),
+	throw(error(instantiation_error,volatile(P))).
+volatile(M:P) :-
+	'$do_volatile'(P,M).
+volatile((G1,G2)) :-
+	'$do_volatile'(G1),
+	'$do_volatile'(G2).
+volatile(P) :-
+	'$current_module'(M),
+	'$do_volatile'(P,M).
+
+'$do_volatile'(P,M) :- dynamic(M:P).
+
 
 :- initialization('$init_thread0').