diff --git a/gtsam/discrete/DecisionTree-inl.h b/gtsam/discrete/DecisionTree-inl.h
index 434a6beac..1f50014d6 100644
--- a/gtsam/discrete/DecisionTree-inl.h
+++ b/gtsam/discrete/DecisionTree-inl.h
@@ -1060,7 +1060,7 @@ namespace gtsam {
   template <typename L, typename Y>
   template <typename A, typename B>
   std::pair<DecisionTree<L, A>, DecisionTree<L, B>> DecisionTree<L, Y>::split(
-      std::function<std::pair<A, B>(const Y&)> AB_of_Y) {
+      std::function<std::pair<A, B>(const Y&)> AB_of_Y) const {
     using AB = std::pair<A, B>;
     const DecisionTree<L, AB> ab(*this, AB_of_Y);
     const DecisionTree<L, A> a(ab, [](const AB& p) { return p.first; });
diff --git a/gtsam/discrete/DecisionTree.h b/gtsam/discrete/DecisionTree.h
index 6a966e0dd..aba5b88b7 100644
--- a/gtsam/discrete/DecisionTree.h
+++ b/gtsam/discrete/DecisionTree.h
@@ -416,7 +416,7 @@ namespace gtsam {
      */
     template <typename A, typename B>
     std::pair<DecisionTree<L, A>, DecisionTree<L, B>> split(
-        std::function<std::pair<A, B>(const Y&)> AB_of_Y);
+        std::function<std::pair<A, B>(const Y&)> AB_of_Y) const;
 
     /// @name Advanced Interface
     /// @{
diff --git a/gtsam/hybrid/HybridGaussianFactorGraph.cpp b/gtsam/hybrid/HybridGaussianFactorGraph.cpp
index 8e6123f10..361cb6e81 100644
--- a/gtsam/hybrid/HybridGaussianFactorGraph.cpp
+++ b/gtsam/hybrid/HybridGaussianFactorGraph.cpp
@@ -390,7 +390,7 @@ HybridGaussianFactorGraph::eliminate(const Ordering &keys) const {
   };
 
   // Perform elimination!
-  ResultTree eliminationResults(prunedProductFactor, eliminate);
+  const ResultTree eliminationResults(prunedProductFactor, eliminate);
 
   // If there are no more continuous parents we create a DiscreteFactor with the
   // error for each discrete choice. Otherwise, create a HybridGaussianFactor