diff --git a/MathLib/Point3d.h b/MathLib/Point3d.h
index 252a74c241d368c7a76646397f96f470f165cbe4..2fb478b34cf1bc002a4600c810c11c03edc211f9 100644
--- a/MathLib/Point3d.h
+++ b/MathLib/Point3d.h
@@ -65,6 +65,7 @@ public:
     double* data() { return x_.data(); }
 
     Eigen::Vector3d const& asEigenVector3d() const { return x_; }
+    Eigen::Vector3d& asEigenVector3d() { return x_; }
 
 private:
     Eigen::Vector3d x_;