diff --git a/gtsam/discrete/DecisionTree-inl.h b/gtsam/discrete/DecisionTree-inl.h
index 1ef3a0e82..cd56780e5 100644
--- a/gtsam/discrete/DecisionTree-inl.h
+++ b/gtsam/discrete/DecisionTree-inl.h
@@ -462,15 +462,17 @@ namespace gtsam {
   // cannot just create a root Choice node on the label: if the label is not the
   // highest label, we need to do a complicated and expensive recursive call.
   template<typename L, typename Y> template<typename Iterator>
-  typename DecisionTree<L, Y>::NodePtr DecisionTree<L, Y>::compose(
-      Iterator begin, Iterator end, const L& label) const {
+  typename DecisionTree<L, Y>::NodePtr DecisionTree<L, Y>::compose(Iterator begin,
+      Iterator end, const L& label) const {
 
     // find highest label among branches
     boost::optional<L> highestLabel;
     boost::optional<size_t> nrChoices;
     for (Iterator it = begin; it != end; it++) {
-      if (it->root_->isLeaf()) continue;
-      boost::shared_ptr<const Choice> c = boost::dynamic_pointer_cast<const Choice> (it->root_);
+      if (it->root_->isLeaf())
+        continue;
+      boost::shared_ptr<const Choice> c =
+          boost::dynamic_pointer_cast<const Choice>(it->root_);
       if (!highestLabel || c->label() > *highestLabel) {
         highestLabel.reset(c->label());
         nrChoices.reset(c->nrChoices());
@@ -483,25 +485,26 @@ namespace gtsam {
       for (Iterator it = begin; it != end; it++)
         choiceOnLabel->push_back(it->root_);
       return Choice::Unique(choiceOnLabel);
-    }
-
-    // Set up a new choice on the highest label
-    boost::shared_ptr<Choice> choiceOnHighestLabel(new Choice(*highestLabel, *nrChoices));
-    // now, for all possible values of highestLabel
-    for (size_t index = 0; index < *nrChoices; index++) {
-      // make a new set of functions for composing by iterating over the given
-      // functions, and selecting the appropriate branch.
-      std::vector<DecisionTree> functions;
-      for (Iterator it = begin; it != end; it++) {
-        // by restricting the input functions to value i for labelBelow
-        DecisionTree chosen = it->choose(*highestLabel, index);
-        functions.push_back(chosen);
+    } else {
+      // Set up a new choice on the highest label
+      boost::shared_ptr<Choice> choiceOnHighestLabel(
+          new Choice(*highestLabel, *nrChoices));
+      // now, for all possible values of highestLabel
+      for (size_t index = 0; index < *nrChoices; index++) {
+        // make a new set of functions for composing by iterating over the given
+        // functions, and selecting the appropriate branch.
+        std::vector<DecisionTree> functions;
+        for (Iterator it = begin; it != end; it++) {
+          // by restricting the input functions to value i for labelBelow
+          DecisionTree chosen = it->choose(*highestLabel, index);
+          functions.push_back(chosen);
+        }
+        // We then recurse, for all values of the highest label
+        NodePtr fi = compose(functions.begin(), functions.end(), label);
+        choiceOnHighestLabel->push_back(fi);
       }
-      // We then recurse, for all values of the highest label
-      NodePtr fi = compose(functions.begin(), functions.end(), label);
-      choiceOnHighestLabel->push_back(fi);
+      return Choice::Unique(choiceOnHighestLabel);
     }
-    return Choice::Unique(choiceOnHighestLabel);
   }
 
   /*********************************************************************************/
@@ -667,9 +670,10 @@ namespace gtsam {
   void DecisionTree<L, Y>::dot(const std::string& name, bool showZero) const {
     std::ofstream os((name + ".dot").c_str());
     dot(os, showZero);
-    system(
+    int result = system(
         ("dot -Tpdf " + name + ".dot -o " + name + ".pdf >& /dev/null").c_str());
-  }
+    if (result==-1) throw std::runtime_error("DecisionTree::dot system call failed");
+}
 
 /*********************************************************************************/