diff --git a/gtsam/hybrid/HybridGaussianProductFactor.h b/gtsam/hybrid/HybridGaussianProductFactor.h
index 508113e87..a06f24423 100644
--- a/gtsam/hybrid/HybridGaussianProductFactor.h
+++ b/gtsam/hybrid/HybridGaussianProductFactor.h
@@ -115,6 +115,16 @@ class GTSAM_EXPORT HybridGaussianProductFactor
   HybridGaussianProductFactor removeEmpty() const;
 
   ///@}
+
+ private:
+#ifdef GTSAM_ENABLE_BOOST_SERIALIZATION
+  /** 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);
+  }
+#endif
 };
 
 // Testable traits
diff --git a/gtsam/hybrid/tests/testSerializationHybrid.cpp b/gtsam/hybrid/tests/testSerializationHybrid.cpp
index 8258d8615..fd92e5cfb 100644
--- a/gtsam/hybrid/tests/testSerializationHybrid.cpp
+++ b/gtsam/hybrid/tests/testSerializationHybrid.cpp
@@ -59,6 +59,9 @@ BOOST_CLASS_EXPORT_GUID(HybridGaussianFactor::FactorValuePairs::Leaf,
 BOOST_CLASS_EXPORT_GUID(HybridGaussianFactor::FactorValuePairs::Choice,
                         "gtsam_HybridGaussianFactor_Factors_Choice");
 
+BOOST_CLASS_EXPORT_GUID(GaussianFactorGraphValuePair,
+                        "gtsam_GaussianFactorGraphValuePair");
+
 BOOST_CLASS_EXPORT_GUID(HybridGaussianConditional,
                         "gtsam_HybridGaussianConditional");
 BOOST_CLASS_EXPORT_GUID(HybridGaussianConditional::Conditionals,