diff --git a/packages/CLPBN/clpbn/aggregates.yap b/packages/CLPBN/clpbn/aggregates.yap
index 90c1ef51e..df3d95de3 100644
--- a/packages/CLPBN/clpbn/aggregates.yap
+++ b/packages/CLPBN/clpbn/aggregates.yap
@@ -11,7 +11,8 @@
 		]).
 
 :- use_module(library(clpbn),
-		[{}/1]).
+		[{}/1,
+		 op(500, xfy, with)]).
 
 :- use_module(library(lists),
 		[last/2,