diff --git a/gtsam/navigation/CombinedImuFactor.cpp b/gtsam/navigation/CombinedImuFactor.cpp
index 7a8c73013..7f58f7e64 100644
--- a/gtsam/navigation/CombinedImuFactor.cpp
+++ b/gtsam/navigation/CombinedImuFactor.cpp
@@ -313,3 +313,6 @@ void CombinedImuFactor::Predict(const Pose3& pose_i, const Vector3& vel_i,
 }
  /// namespace gtsam
 
+/// Boost serialization export definition for derived class
+BOOST_CLASS_EXPORT_IMPLEMENT(gtsam::PreintegrationCombinedParams);
+
diff --git a/gtsam/navigation/CombinedImuFactor.h b/gtsam/navigation/CombinedImuFactor.h
index f7ea25371..8b6dcd3f2 100644
--- a/gtsam/navigation/CombinedImuFactor.h
+++ b/gtsam/navigation/CombinedImuFactor.h
@@ -384,3 +384,5 @@ struct traits<CombinedImuFactor> : public Testable<CombinedImuFactor> {};
 
 }  // namespace gtsam
 
+/// Add Boost serialization export key (declaration) for derived class
+BOOST_CLASS_EXPORT_KEY(gtsam::PreintegrationCombinedParams);
diff --git a/gtsam/navigation/tests/testImuFactorSerialization.cpp b/gtsam/navigation/tests/testImuFactorSerialization.cpp
index 6a9e727f2..ed72e18e9 100644
--- a/gtsam/navigation/tests/testImuFactorSerialization.cpp
+++ b/gtsam/navigation/tests/testImuFactorSerialization.cpp
@@ -42,9 +42,6 @@ BOOST_CLASS_EXPORT_GUID(gtsam::noiseModel::Isotropic,
 BOOST_CLASS_EXPORT_GUID(gtsam::SharedNoiseModel, "gtsam_SharedNoiseModel");
 BOOST_CLASS_EXPORT_GUID(gtsam::SharedDiagonal, "gtsam_SharedDiagonal");
 
-/// Add Boost serialization export for derived class
-BOOST_CLASS_EXPORT_GUID(gtsam::PreintegrationCombinedParams, "gtsam_PreintegrationCombinedParams");
-
 template <typename P>
 P getPreintegratedMeasurements() {
   // Create default parameters with Z-down and above noise paramaters