diff --git a/gtsam/hybrid/HybridBayesTree.cpp b/gtsam/hybrid/HybridBayesTree.cpp
index 8fdedab44..c9c6afa79 100644
--- a/gtsam/hybrid/HybridBayesTree.cpp
+++ b/gtsam/hybrid/HybridBayesTree.cpp
@@ -73,6 +73,8 @@ struct HybridAssignmentData {
   GaussianBayesTree::sharedNode parentClique_;
   // The gaussian bayes tree that will be recursively created.
   GaussianBayesTree* gaussianbayesTree_;
+  // Flag indicating if all the nodes are valid. Used in optimize().
+  bool valid_;
 
   /**
    * @brief Construct a new Hybrid Assignment Data object.
@@ -83,10 +85,13 @@ struct HybridAssignmentData {
    */
   HybridAssignmentData(const DiscreteValues& assignment,
                        const GaussianBayesTree::sharedNode& parentClique,
-                       GaussianBayesTree* gbt)
+                       GaussianBayesTree* gbt, bool valid = true)
       : assignment_(assignment),
         parentClique_(parentClique),
-        gaussianbayesTree_(gbt) {}
+        gaussianbayesTree_(gbt),
+        valid_(valid) {}
+
+  bool isValid() const { return valid_; }
 
   /**
    * @brief A function used during tree traversal that operates on each node
@@ -101,6 +106,7 @@ struct HybridAssignmentData {
       HybridAssignmentData& parentData) {
     // Extract the gaussian conditional from the Hybrid clique
     HybridConditional::shared_ptr hybrid_conditional = node->conditional();
+
     GaussianConditional::shared_ptr conditional;
     if (hybrid_conditional->isHybrid()) {
       conditional = (*hybrid_conditional->asMixture())(parentData.assignment_);
@@ -111,15 +117,21 @@ struct HybridAssignmentData {
       conditional = boost::make_shared<GaussianConditional>();
     }
 
-    // Create the GaussianClique for the current node
-    auto clique = boost::make_shared<GaussianBayesTree::Node>(conditional);
-    // Add the current clique to the GaussianBayesTree.
-    parentData.gaussianbayesTree_->addClique(clique, parentData.parentClique_);
+    GaussianBayesTree::sharedNode clique;
+    if (conditional) {
+      // Create the GaussianClique for the current node
+      clique = boost::make_shared<GaussianBayesTree::Node>(conditional);
+      // Add the current clique to the GaussianBayesTree.
+      parentData.gaussianbayesTree_->addClique(clique,
+                                               parentData.parentClique_);
+    } else {
+      parentData.valid_ = false;
+    }
 
     // Create new HybridAssignmentData where the current node is the parent
     // This will be passed down to the children nodes
     HybridAssignmentData data(parentData.assignment_, clique,
-                              parentData.gaussianbayesTree_);
+                              parentData.gaussianbayesTree_, parentData.valid_);
     return data;
   }
 };
@@ -138,6 +150,9 @@ VectorValues HybridBayesTree::optimize(const DiscreteValues& assignment) const {
         visitorPost);
   }
 
+  if (!rootData.isValid()) {
+    return VectorValues();
+  }
   VectorValues result = gbt.optimize();
 
   // Return the optimized bayes net result.
@@ -151,6 +166,8 @@ void HybridBayesTree::prune(const size_t maxNrLeaves) {
 
   DecisionTreeFactor prunedDecisionTree = decisionTree->prune(maxNrLeaves);
   decisionTree->root_ = prunedDecisionTree.root_;
+  // this->print();
+  // decisionTree->print("", DefaultKeyFormatter);
 
   /// Helper struct for pruning the hybrid bayes tree.
   struct HybridPrunerData {