diff --git a/changes-5.1.html b/changes-5.1.html
index 4eeab30ee..5af3709ae 100644
--- a/changes-5.1.html
+++ b/changes-5.1.html
@@ -17,6 +17,9 @@ xb
 
 <h2>Yap-5.1.3:</h2>
 <ul>
+<li> FIXED: handle message_queue_create/1 with vars right (obs from
+  Paulo Moura).</li>
+<li> FIXED: handle thread overflow right (obs from Paulo Moura).</li>
 <li> NEW: upgrade clpqr and chr (SWI compatibility).</li>
 <li> NEW: expects_dialect/1 directive (SWI compatibility).</li>
 <li> NEW: terms:unifiable/3 (SWI compatibility).</li>
diff --git a/pl/threads.yap b/pl/threads.yap
index 712903ed9..e52ecbc41 100644
--- a/pl/threads.yap
+++ b/pl/threads.yap
@@ -570,8 +570,8 @@ message_queue_create(Name) :-
 '$create_mq'(Name) :-
 	'$new_mutex'(Mutex),
 	'$cond_create'(Cond),
-	'$mq_iname'(Name, CName),
 	'$global_queue_mutex'(QMutex),
+	'$mq_iname'(Name, CName),
 	'$lock_mutex'(QMutex),
 	( recorded('$queue',q(Name,_,_, _),_) ->
 	  '$unlock_mutex'(QMutex),
@@ -583,11 +583,21 @@ message_queue_create(Name) :-
 
 '$mq_iname'(I,X) :-
 	integer(I), !,
-	number_codes(I,Codes),
-	atom_codes(X, [0'$,0'M,0'Q,0'_|Codes]).
+	atomic_concat('$MQ_NAME_KEY_',I,X).
+'$mq_iname'(A,X) :-
+	var(A), !,
+	'$integers'(I),
+	atomic_concat(message_queue_,I,A),
+	atomic_concat('$MQ_NAME_KEY_',A,X),
+	\+ recorded('$queue',q(A,_,_, X),_), !.
 '$mq_iname'(A,X) :-
 	atom_concat('$MQ_NAME_KEY_',A,X).
 
+'$integers'(0).
+'$integers'(I) :-
+	'$integers'(I1),
+	I is I1+1.
+
 	
 message_queue_destroy(Name) :-
 	var(Name), !,