diff --git a/gtsam/hybrid/HybridDiscreteFactor.cpp b/gtsam/hybrid/HybridDiscreteFactor.cpp
index 605ea5738..dd8b867be 100644
--- a/gtsam/hybrid/HybridDiscreteFactor.cpp
+++ b/gtsam/hybrid/HybridDiscreteFactor.cpp
@@ -40,8 +40,10 @@ HybridDiscreteFactor::HybridDiscreteFactor(DecisionTreeFactor &&dtf)
 /* ************************************************************************ */
 bool HybridDiscreteFactor::equals(const HybridFactor &lf, double tol) const {
   const This *e = dynamic_cast<const This *>(&lf);
-  // TODO(Varun) How to compare inner_ when they are abstract types?
-  return e != nullptr && Base::equals(*e, tol);
+  if (e == nullptr) return false;
+  if (!Base::equals(*e, tol)) return false;
+  return inner_ ? (e->inner_ ? inner_->equals(*(e->inner_), tol) : false)
+                : !(e->inner_);
 }
 
 /* ************************************************************************ */
diff --git a/gtsam/hybrid/HybridDiscreteFactor.h b/gtsam/hybrid/HybridDiscreteFactor.h
index 7ac97443a..7a43ab3a5 100644
--- a/gtsam/hybrid/HybridDiscreteFactor.h
+++ b/gtsam/hybrid/HybridDiscreteFactor.h
@@ -45,6 +45,9 @@ class GTSAM_EXPORT HybridDiscreteFactor : public HybridFactor {
   /// @name Constructors
   /// @{
 
+  /// Default constructor - for serialization.
+  HybridDiscreteFactor() = default;
+
   // Implicit conversion from a shared ptr of DF
   HybridDiscreteFactor(DiscreteFactor::shared_ptr other);
 
@@ -70,6 +73,15 @@ class GTSAM_EXPORT HybridDiscreteFactor : public HybridFactor {
   /// Return the error of the underlying Discrete Factor.
   double error(const HybridValues &values) const override;
   /// @}
+
+ private:
+  /** Serialization function */
+  friend class boost::serialization::access;
+  template <class ARCHIVE>
+  void serialize(ARCHIVE &ar, const unsigned int /*version*/) {
+    ar &BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
+    ar &BOOST_SERIALIZATION_NVP(inner_);
+  }
 };
 
 // traits
diff --git a/gtsam/hybrid/HybridGaussianFactor.cpp b/gtsam/hybrid/HybridGaussianFactor.cpp
index 5a89a04a8..4fe18bea7 100644
--- a/gtsam/hybrid/HybridGaussianFactor.cpp
+++ b/gtsam/hybrid/HybridGaussianFactor.cpp
@@ -44,15 +44,21 @@ HybridGaussianFactor::HybridGaussianFactor(HessianFactor &&hf)
 /* ************************************************************************* */
 bool HybridGaussianFactor::equals(const HybridFactor &other, double tol) const {
   const This *e = dynamic_cast<const This *>(&other);
-  // TODO(Varun) How to compare inner_ when they are abstract types?
-  return e != nullptr && Base::equals(*e, tol);
+  if (e == nullptr) return false;
+  if (!Base::equals(*e, tol)) return false;
+  return inner_ ? (e->inner_ ? inner_->equals(*(e->inner_), tol) : false)
+                : !(e->inner_);
 }
 
 /* ************************************************************************* */
 void HybridGaussianFactor::print(const std::string &s,
                                  const KeyFormatter &formatter) const {
   HybridFactor::print(s, formatter);
-  inner_->print("\n", formatter);
+  if (inner_) {
+    inner_->print("\n", formatter);
+  } else {
+    std::cout << "\nGaussian: nullptr" << std::endl;
+  }
 };
 
 /* ************************************************************************ */
diff --git a/gtsam/hybrid/HybridGaussianFactor.h b/gtsam/hybrid/HybridGaussianFactor.h
index 6d179d1c1..6bb022396 100644
--- a/gtsam/hybrid/HybridGaussianFactor.h
+++ b/gtsam/hybrid/HybridGaussianFactor.h
@@ -43,6 +43,10 @@ class GTSAM_EXPORT HybridGaussianFactor : public HybridFactor {
   using This = HybridGaussianFactor;
   using shared_ptr = boost::shared_ptr<This>;
 
+  /// @name Constructors
+  /// @{
+
+  /// Default constructor - for serialization.
   HybridGaussianFactor() = default;
 
   /**
@@ -79,7 +83,7 @@ class GTSAM_EXPORT HybridGaussianFactor : public HybridFactor {
    */
   explicit HybridGaussianFactor(HessianFactor &&hf);
 
- public:
+  /// @}
   /// @name Testable
   /// @{
 
@@ -101,6 +105,15 @@ class GTSAM_EXPORT HybridGaussianFactor : public HybridFactor {
   /// Return the error of the underlying Gaussian factor.
   double error(const HybridValues &values) const override;
   /// @}
+
+ private:
+  /** Serialization function */
+  friend class boost::serialization::access;
+  template <class ARCHIVE>
+  void serialize(ARCHIVE &ar, const unsigned int /*version*/) {
+    ar &BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
+    ar &BOOST_SERIALIZATION_NVP(inner_);
+  }
 };
 
 // traits