diff --git a/gtsam/navigation/AHRSFactor.h b/gtsam/navigation/AHRSFactor.h
index c2a88bd44..8ed695622 100644
--- a/gtsam/navigation/AHRSFactor.h
+++ b/gtsam/navigation/AHRSFactor.h
@@ -38,13 +38,13 @@ class GTSAM_EXPORT PreintegratedAhrsMeasurements : public PreintegratedRotation
   Vector3 biasHat_; ///< Angular rate bias values used during preintegration.
   Matrix3 preintMeasCov_; ///< Covariance matrix of the preintegrated measurements (first-order propagation from *measurementCovariance*)
 
-  /// Default constructor, only for serialization
-  PreintegratedAhrsMeasurements() {}
-
   friend class AHRSFactor;
 
  public:
 
+  /// Default constructor, only for serialization and Cython wrapper
+  PreintegratedAhrsMeasurements() {}
+
   /**
    *  Default constructor, initialize with no measurements
    *  @param bias Current estimate of acceleration and rotation rate biases
diff --git a/gtsam/navigation/CombinedImuFactor.h b/gtsam/navigation/CombinedImuFactor.h
index bcad9d8f7..99c45ff34 100644
--- a/gtsam/navigation/CombinedImuFactor.h
+++ b/gtsam/navigation/CombinedImuFactor.h
@@ -115,7 +115,6 @@ public:
    */
   Eigen::Matrix<double, 15, 15> preintMeasCov_;
 
-  PreintegratedCombinedMeasurements() {}
 
   friend class CombinedImuFactor;
 
@@ -123,6 +122,9 @@ public:
   /// @name Constructors
   /// @{
 
+  /// Default constructor only for serialization and Cython wrapper
+  PreintegratedCombinedMeasurements() {}
+
   /**
    *  Default constructor, initializes the class with no measurements
    *  @param bias Current estimate of acceleration and rotation rate biases
diff --git a/gtsam/navigation/ImuFactor.h b/gtsam/navigation/ImuFactor.h
index 532abdac0..55f043dd3 100644
--- a/gtsam/navigation/ImuFactor.h
+++ b/gtsam/navigation/ImuFactor.h
@@ -78,13 +78,13 @@ protected:
   Matrix9 preintMeasCov_; ///< COVARIANCE OF: [PreintPOSITION PreintVELOCITY PreintROTATION]
   ///< (first-order propagation from *measurementCovariance*).
 
-  /// Default constructor for serialization
+public:
+
+  /// Default constructor for serialization and Cython wrapper
   PreintegratedImuMeasurements() {
     preintMeasCov_.setZero();
   }
 
-public:
-
  /**
    *  Constructor, initializes the class with no measurements
    *  @param bias Current estimate of acceleration and rotation rate biases
diff --git a/gtsam/nonlinear/Marginals.h b/gtsam/nonlinear/Marginals.h
index ddf164cb4..16e7de892 100644
--- a/gtsam/nonlinear/Marginals.h
+++ b/gtsam/nonlinear/Marginals.h
@@ -48,6 +48,10 @@ protected:
 
 public:
 
+  /// Default constructor only for Cython wrapper
+  Marginals(){}
+
+  /// Copy constructor
   Marginals(const Marginals&) = default;
 
   /** Construct a marginals class.
@@ -93,6 +97,10 @@ protected:
   FastMap<Key, size_t> indices_;
 
 public:
+  /// Default constructor only for Cython wrapper
+  JointMarginal() {}
+
+  /// Copy constructor
   JointMarginal(const JointMarginal&) = default;
 
   /** Access a block, corresponding to a pair of variables, of the joint