diff --git a/gtsam/discrete/DecisionTree-inl.h b/gtsam/discrete/DecisionTree-inl.h
index ab14b2a72..84116ccd5 100644
--- a/gtsam/discrete/DecisionTree-inl.h
+++ b/gtsam/discrete/DecisionTree-inl.h
@@ -604,7 +604,7 @@ namespace gtsam {
     using MXChoice = typename DecisionTree<M, X>::Choice;
     auto choice = boost::dynamic_pointer_cast<const MXChoice>(f);
     if (!choice) throw std::invalid_argument(
-        "DecisionTree::Convert: Invalid NodePtr");
+        "DecisionTree::convertFrom: Invalid NodePtr");
 
     // get new label
     const M oldLabel = choice->label();
@@ -634,6 +634,8 @@ namespace gtsam {
 
       using Choice = typename DecisionTree<L, Y>::Choice;
       auto choice = boost::dynamic_pointer_cast<const Choice>(node);
+      if (!choice)
+        throw std::invalid_argument("DecisionTree::Visit: Invalid NodePtr");
       for (auto&& branch : choice->branches()) (*this)(branch);  // recurse!
     }
   };
@@ -663,6 +665,8 @@ namespace gtsam {
 
       using Choice = typename DecisionTree<L, Y>::Choice;
       auto choice = boost::dynamic_pointer_cast<const Choice>(node);
+      if (!choice)
+        throw std::invalid_argument("DecisionTree::VisitWith: Invalid NodePtr");
       for (size_t i = 0; i < choice->nrChoices(); i++) {
         choices[choice->label()] = i;    // Set assignment for label to i
         (*this)(choice->branches()[i]);  // recurse!
diff --git a/gtsam/discrete/DecisionTree.h b/gtsam/discrete/DecisionTree.h
index 9692094e1..78f3a75b7 100644
--- a/gtsam/discrete/DecisionTree.h
+++ b/gtsam/discrete/DecisionTree.h
@@ -38,7 +38,7 @@ namespace gtsam {
    * Y = function range (any algebra), e.g., bool, int, double
    */
   template<typename L, typename Y>
-  class GTSAM_EXPORT DecisionTree {
+  class DecisionTree {
 
    protected:
     /// Default method for comparison of two objects of type Y.
@@ -340,4 +340,11 @@ namespace gtsam {
     return f.apply(g, op);
   }
 
+  /// unzip a DecisionTree if its leaves are `std::pair`
+  template<typename L, typename T1, typename T2>
+  std::pair<DecisionTree<L, T1>, DecisionTree<L, T2> > unzip(const DecisionTree<L, std::pair<T1, T2> > &input) {
+    return std::make_pair(DecisionTree<L, T1>(input, [](std::pair<T1, T2> i) { return i.first; }),
+                          DecisionTree<L, T2>(input, [](std::pair<T1, T2> i) { return i.second; }));
+  }
+
 } // namespace gtsam