diff --git a/packages/ProbLog/problog/tptree.yap b/packages/ProbLog/problog/tptree.yap
index a8f0aa935..c6e4d0740 100644
--- a/packages/ProbLog/problog/tptree.yap
+++ b/packages/ProbLog/problog/tptree.yap
@@ -247,7 +247,7 @@
 % load library modules
 :- use_module(library(tries)).
 :- use_module(library(lists), [append/3, member/2, memberchk/2, delete/3]).
-:- use_module(library(system), [delete_file/1, shell/1]).
+:- use_module(library(system), [delete_file/1, shell/1, tmpnam/1]).
 :- use_module(library(ordsets), [ord_intersection/3, ord_union/3]).
 
 % load our own modules