diff --git a/gtsam/hybrid/HybridGaussianConditional.cpp b/gtsam/hybrid/HybridGaussianConditional.cpp
index df59637aa5..0b1dc53377 100644
--- a/gtsam/hybrid/HybridGaussianConditional.cpp
+++ b/gtsam/hybrid/HybridGaussianConditional.cpp
@@ -28,23 +28,37 @@
 #include <gtsam/linear/GaussianFactorGraph.h>
 
 namespace gtsam {
+HybridGaussianFactor::FactorValuePairs GetFactorValuePairs(
+    const HybridGaussianConditional::Conditionals &conditionals) {
+  auto func = [](const GaussianConditional::shared_ptr &conditional)
+      -> GaussianFactorValuePair {
+    double value = 0.0;
+    // Check if conditional is pruned
+    if (conditional) {
+      // Assign log(\sqrt(|2πΣ|)) = -log(1 / sqrt(|2πΣ|))
+      value = -conditional->logNormalizationConstant();
+    }
+    return {std::dynamic_pointer_cast<GaussianFactor>(conditional), value};
+  };
+  return HybridGaussianFactor::FactorValuePairs(conditionals, func);
+}
 
 HybridGaussianConditional::HybridGaussianConditional(
     const KeyVector &continuousFrontals, const KeyVector &continuousParents,
     const DiscreteKeys &discreteParents,
     const HybridGaussianConditional::Conditionals &conditionals)
     : BaseFactor(CollectKeys(continuousFrontals, continuousParents),
-                 discreteParents),
+                 discreteParents, GetFactorValuePairs(conditionals)),
       BaseConditional(continuousFrontals.size()),
       conditionals_(conditionals) {
-  // Calculate logConstant_ as the maximum of the log constants of the
+  // Calculate logConstant_ as the minimum of the log normalizers of the
   // conditionals, by visiting the decision tree:
-  logConstant_ = -std::numeric_limits<double>::infinity();
+  logConstant_ = std::numeric_limits<double>::infinity();
   conditionals_.visit(
       [this](const GaussianConditional::shared_ptr &conditional) {
         if (conditional) {
-          this->logConstant_ = std::max(
-              this->logConstant_, conditional->logNormalizationConstant());
+          this->logConstant_ = std::min(
+              this->logConstant_, -conditional->logNormalizationConstant());
         }
       });
 }
@@ -64,21 +78,6 @@ HybridGaussianConditional::HybridGaussianConditional(
                                 DiscreteKeys{discreteParent},
                                 Conditionals({discreteParent}, conditionals)) {}
 
-/* *******************************************************************************/
-// TODO(dellaert): This is copy/paste: HybridGaussianConditional should be
-// derived from HybridGaussianFactor, no?
-GaussianFactorGraphTree HybridGaussianConditional::add(
-    const GaussianFactorGraphTree &sum) const {
-  using Y = GaussianFactorGraph;
-  auto add = [](const Y &graph1, const Y &graph2) {
-    auto result = graph1;
-    result.push_back(graph2);
-    return result;
-  };
-  const auto tree = asGaussianFactorGraphTree();
-  return sum.empty() ? tree : sum.apply(tree, add);
-}
-
 /* *******************************************************************************/
 GaussianFactorGraphTree HybridGaussianConditional::asGaussianFactorGraphTree()
     const {
@@ -86,7 +85,7 @@ GaussianFactorGraphTree HybridGaussianConditional::asGaussianFactorGraphTree()
     // First check if conditional has not been pruned
     if (gc) {
       const double Cgm_Kgcm =
-          this->logConstant_ - gc->logNormalizationConstant();
+          -this->logConstant_ - gc->logNormalizationConstant();
       // If there is a difference in the covariances, we need to account for
       // that since the error is dependent on the mode.
       if (Cgm_Kgcm > 0.0) {
@@ -157,7 +156,8 @@ void HybridGaussianConditional::print(const std::string &s,
     std::cout << "(" << formatter(dk.first) << ", " << dk.second << "), ";
   }
   std::cout << std::endl
-            << " logNormalizationConstant: " << logConstant_ << std::endl
+            << " logNormalizationConstant: " << logNormalizationConstant()
+            << std::endl
             << std::endl;
   conditionals_.print(
       "", [&](Key k) { return formatter(k); },
@@ -216,7 +216,7 @@ std::shared_ptr<HybridGaussianFactor> HybridGaussianConditional::likelihood(
           -> GaussianFactorValuePair {
         const auto likelihood_m = conditional->likelihood(given);
         const double Cgm_Kgcm =
-            logConstant_ - conditional->logNormalizationConstant();
+            -logConstant_ - conditional->logNormalizationConstant();
         if (Cgm_Kgcm == 0.0) {
           return {likelihood_m, 0.0};
         } else {
@@ -330,7 +330,7 @@ double HybridGaussianConditional::conditionalError(
   // Check if valid pointer
   if (conditional) {
     return conditional->error(continuousValues) +  //
-           logConstant_ - conditional->logNormalizationConstant();
+           -logConstant_ - conditional->logNormalizationConstant();
   } else {
     // If not valid, pointer, it means this conditional was pruned,
     // so we return maximum error.
diff --git a/gtsam/hybrid/HybridGaussianConditional.h b/gtsam/hybrid/HybridGaussianConditional.h
index eb2bbb9378..72a9994729 100644
--- a/gtsam/hybrid/HybridGaussianConditional.h
+++ b/gtsam/hybrid/HybridGaussianConditional.h
@@ -51,20 +51,22 @@ class HybridValues;
  * @ingroup hybrid
  */
 class GTSAM_EXPORT HybridGaussianConditional
-    : public HybridFactor,
-      public Conditional<HybridFactor, HybridGaussianConditional> {
+    : public HybridGaussianFactor,
+      public Conditional<HybridGaussianFactor, HybridGaussianConditional> {
  public:
   using This = HybridGaussianConditional;
-  using shared_ptr = std::shared_ptr<HybridGaussianConditional>;
-  using BaseFactor = HybridFactor;
-  using BaseConditional = Conditional<HybridFactor, HybridGaussianConditional>;
+  using shared_ptr = std::shared_ptr<This>;
+  using BaseFactor = HybridGaussianFactor;
+  using BaseConditional = Conditional<BaseFactor, HybridGaussianConditional>;
 
   /// typedef for Decision Tree of Gaussian Conditionals
   using Conditionals = DecisionTree<Key, GaussianConditional::shared_ptr>;
 
  private:
   Conditionals conditionals_;  ///< a decision tree of Gaussian conditionals.
-  double logConstant_;         ///< log of the normalization constant.
+  ///< Negative-log of the normalization constant (log(\sqrt(|2πΣ|))).
+  ///< Take advantage of the neg-log space so everything is a minimization
+  double logConstant_;
 
   /**
    * @brief Convert a HybridGaussianConditional of conditionals into
@@ -107,8 +109,9 @@ class GTSAM_EXPORT HybridGaussianConditional
                             const Conditionals &conditionals);
 
   /**
-   * @brief Make a Hybrid Gaussian Conditional from a vector of Gaussian conditionals.
-   * The DecisionTree-based constructor is preferred over this one.
+   * @brief Make a Hybrid Gaussian Conditional from a vector of Gaussian
+   * conditionals. The DecisionTree-based constructor is preferred over this
+   * one.
    *
    * @param continuousFrontals The continuous frontal variables
    * @param continuousParents The continuous parent variables
@@ -149,7 +152,7 @@ class GTSAM_EXPORT HybridGaussianConditional
 
   /// The log normalization constant is max of the the individual
   /// log-normalization constants.
-  double logNormalizationConstant() const override { return logConstant_; }
+  double logNormalizationConstant() const override { return -logConstant_; }
 
   /**
    * Create a likelihood factor for a hybrid Gaussian conditional,
@@ -232,14 +235,6 @@ class GTSAM_EXPORT HybridGaussianConditional
    */
   void prune(const DecisionTreeFactor &discreteProbs);
 
-  /**
-   * @brief Merge the Gaussian Factor Graphs in `this` and `sum` while
-   * maintaining the decision tree structure.
-   *
-   * @param sum Decision Tree of Gaussian Factor Graphs
-   * @return GaussianFactorGraphTree
-   */
-  GaussianFactorGraphTree add(const GaussianFactorGraphTree &sum) const;
   /// @}
 
  private:
diff --git a/gtsam/hybrid/tests/testHybridGaussianConditional.cpp b/gtsam/hybrid/tests/testHybridGaussianConditional.cpp
index 406203db84..dde493685b 100644
--- a/gtsam/hybrid/tests/testHybridGaussianConditional.cpp
+++ b/gtsam/hybrid/tests/testHybridGaussianConditional.cpp
@@ -100,7 +100,7 @@ TEST(HybridGaussianConditional, Error) {
   auto actual = hybrid_conditional.errorTree(vv);
 
   // Check result.
-  std::vector<DiscreteKey> discrete_keys = {mode};
+  DiscreteKeys discrete_keys{mode};
   std::vector<double> leaves = {conditionals[0]->error(vv),
                                 conditionals[1]->error(vv)};
   AlgebraicDecisionTree<Key> expected(discrete_keys, leaves);
@@ -172,6 +172,37 @@ TEST(HybridGaussianConditional, ContinuousParents) {
   EXPECT(continuousParentKeys[0] == X(0));
 }
 
+/* ************************************************************************* */
+/// Check error with mode dependent constants.
+TEST(HybridGaussianConditional, Error2) {
+  using namespace mode_dependent_constants;
+  auto actual = hybrid_conditional.errorTree(vv);
+
+  // Check result.
+  DiscreteKeys discrete_keys{mode};
+  double logNormalizer0 = -conditionals[0]->logNormalizationConstant();
+  double logNormalizer1 = -conditionals[1]->logNormalizationConstant();
+  double minLogNormalizer = std::min(logNormalizer0, logNormalizer1);
+
+  // Expected error is e(X) + log(|2πΣ|).
+  // We normalize log(|2πΣ|) with min(logNormalizers) so it is non-negative.
+  std::vector<double> leaves = {
+      conditionals[0]->error(vv) + logNormalizer0 - minLogNormalizer,
+      conditionals[1]->error(vv) + logNormalizer1 - minLogNormalizer};
+  AlgebraicDecisionTree<Key> expected(discrete_keys, leaves);
+
+  EXPECT(assert_equal(expected, actual, 1e-6));
+
+  // Check for non-tree version.
+  for (size_t mode : {0, 1}) {
+    const HybridValues hv{vv, {{M(0), mode}}};
+    EXPECT_DOUBLES_EQUAL(conditionals[mode]->error(vv) -
+                             conditionals[mode]->logNormalizationConstant() -
+                             minLogNormalizer,
+                         hybrid_conditional.error(hv), 1e-8);
+  }
+}
+
 /* ************************************************************************* */
 /// Check that the likelihood is proportional to the conditional density given
 /// the measurements.