diff --git a/packages/CLPBN/clpbn/ground_factors.yap b/packages/CLPBN/clpbn/ground_factors.yap
index 584068019..4454b64b2 100644
--- a/packages/CLPBN/clpbn/ground_factors.yap
+++ b/packages/CLPBN/clpbn/ground_factors.yap
@@ -142,6 +142,7 @@ add_factor(factor(Type, Id, Ks, _, _Phi, Constraints), NKs) :-
     %writeln(+Ks),
 	( Ks = [K,Els], var(Els)
 	 ->
+	% aggregate factor
 	  once(run(Constraints)),
 	  avg_factors(K, Els, 0.0, NewKeys, NewId),
 	  NKs = [K|NewKeys]
@@ -150,8 +151,13 @@ add_factor(factor(Type, Id, Ks, _, _Phi, Constraints), NKs) :-
 	  NKs = Ks,
 	  Id = NewId
 	),
-	\+ f(Type, NewId, NKs),
-	assert(f(Type, NewId, NKs)).
+	(
+          f(Type, NewId, NKs)
+        ->
+	  true
+        ;
+	  assert(f(Type, NewId, NKs))
+         ).
 
 run([Goal|Goals]) :-
 	call(user:Goal),
diff --git a/packages/real b/packages/real
index 4d3759739..6575e08bd 160000
--- a/packages/real
+++ b/packages/real
@@ -1 +1 @@
-Subproject commit 4d3759739bd256a5a2d0c75ae4921c9147ad5d30
+Subproject commit 6575e08bd063e0d0476a1bdbfe216684b4d5e6e4