diff --git a/cpp/BinaryConditional.h b/cpp/BinaryConditional.h
index 0a9001d40..064587e9a 100644
--- a/cpp/BinaryConditional.h
+++ b/cpp/BinaryConditional.h
@@ -54,15 +54,19 @@ namespace gtsam {
 		BinaryConditional(const std::string& key, const std::string& parent, const std::vector<double>& cpt) :
 			Conditional(key) {
 			parents_.push_back(parent);
-			cpt_ = cpt;
+			for( int i = 0 ; i < cpt.size() ; i++ )
+				cpt_.push_back(1-cpt[i]); // p(!x|parents)
+			cpt_.insert(cpt_.end(),cpt.begin(),cpt.end()); // p(x|parents)
 		}
 
 		double probability( std::map<std::string,bool> config) {
-			int index = 0, count = 0;
-			BOOST_FOREACH( std::string parent, parents_)
-				index += pow(2,count++)*(int)(config[parent]);
+			int index = 0, count = 1;
+			BOOST_FOREACH( std::string parent, parents_){
+				index += count*(int)(config[parent]);
+				count = count << 1;
+			}
 			if( config.find(key_)->second )
-				index += pow(2,count);
+				index += count;
 			return cpt_[index];
 		}
 
diff --git a/cpp/testBinaryBayesNet.cpp b/cpp/testBinaryBayesNet.cpp
index 131b0c01b..2b67939e7 100644
--- a/cpp/testBinaryBayesNet.cpp
+++ b/cpp/testBinaryBayesNet.cpp
@@ -31,7 +31,7 @@ using namespace gtsam;
 /** A Bayes net made from binary conditional probability tables */
 typedef BayesNet<BinaryConditional> BinaryBayesNet;
 
-/* ************************************************************************* */
+/************************************************************************** */
 TEST( BinaryBayesNet, constructor )
 {
 	// small Bayes Net x <- y
@@ -40,19 +40,19 @@ TEST( BinaryBayesNet, constructor )
 	// p(x|y=1) = 0.6
 
 	map<string,bool> config;
-	config["y"] = false;
-	config["x"] = false;
+	config["y"] = true;
+	config["x"] = true;
 	// unary conditional for y
 	boost::shared_ptr<BinaryConditional> py(new BinaryConditional("y",0.2));
 	py->print("py");
-	DOUBLES_EQUAL(0.8,py->probability(config),0.01);
+	DOUBLES_EQUAL(0.2,py->probability(config),0.01);
 
 	// single parent conditional for x
 	vector<double> cpt;
-	cpt += 0.7, 0.4, 0.3, 0.6 ; // array index corresponds to binary parent configuration
+	cpt += 0.3, 0.6 ; // array index corresponds to binary parent configuration
 	boost::shared_ptr<BinaryConditional> px_y(new BinaryConditional("x","y",cpt));
 	px_y->print("px_y");
-	DOUBLES_EQUAL(0.7,px_y->probability(config),0.01);
+	DOUBLES_EQUAL(0.6,px_y->probability(config),0.01);
 
 	// push back conditionals in topological sort order (parents last)
 	BinaryBayesNet bbn;