diff --git a/cmake/HandleEigen.cmake b/cmake/HandleEigen.cmake
index b3b4f66b6..651cd1009 100644
--- a/cmake/HandleEigen.cmake
+++ b/cmake/HandleEigen.cmake
@@ -59,7 +59,12 @@ else()
 endif()

 # Detect Eigen version:
-set(EIGEN_VER_H "${GTSAM_EIGEN_INCLUDE_FOR_BUILD}/Eigen/src/Core/util/Macros.h")
+# Since Eigen 5.0.0 the version macros moved from Eigen/src/Core/util/Macros.h
+# to a dedicated Eigen/Version header, so check the new location first.
+set(EIGEN_VER_H "${GTSAM_EIGEN_INCLUDE_FOR_BUILD}/Eigen/Version")
+if (NOT EXISTS ${EIGEN_VER_H})
+    set(EIGEN_VER_H "${GTSAM_EIGEN_INCLUDE_FOR_BUILD}/Eigen/src/Core/util/Macros.h")
+endif()
 if (EXISTS ${EIGEN_VER_H})
     file(READ "${EIGEN_VER_H}" STR_EIGEN_VERSION)

diff --git a/gtsam/base/Matrix.h b/gtsam/base/Matrix.h
index cfedf6d8c..9c9771407 100644
--- a/gtsam/base/Matrix.h
+++ b/gtsam/base/Matrix.h
@@ -54,7 +54,7 @@ using Matrix7##N = Eigen::Matrix<double, 7, N>;  \
 using Matrix8##N = Eigen::Matrix<double, 8, N>;  \
 using Matrix9##N = Eigen::Matrix<double, 9, N>;  \
 static const Eigen::MatrixBase<Matrix##N>::IdentityReturnType I_##N##x##N = Matrix##N::Identity(); \
-static const Eigen::MatrixBase<Matrix##N>::ConstantReturnType Z_##N##x##N = Matrix##N::Zero();
+static const decltype(Matrix##N::Zero()) Z_##N##x##N = Matrix##N::Zero();

 GTSAM_MAKE_MATRIX_DEFS(1)
 GTSAM_MAKE_MATRIX_DEFS(2)
diff --git a/gtsam/base/Vector.h b/gtsam/base/Vector.h
index f7923ff88..5410393f6 100644
--- a/gtsam/base/Vector.h
+++ b/gtsam/base/Vector.h
@@ -27,6 +27,7 @@

 #include <gtsam/global_includes.h>
 #include <Eigen/Core>
+#include <cassert>
 #include <iosfwd>
 #include <list>

@@ -42,14 +43,14 @@ typedef Eigen::Matrix<double, 1, 1> Vector1;
 typedef Eigen::Vector2d Vector2;
 typedef Eigen::Vector3d Vector3;

-static const Eigen::MatrixBase<Vector2>::ConstantReturnType Z_2x1 = Vector2::Zero();
-static const Eigen::MatrixBase<Vector3>::ConstantReturnType Z_3x1 = Vector3::Zero();
+static const decltype(Vector2::Zero()) Z_2x1 = Vector2::Zero();
+static const decltype(Vector3::Zero()) Z_3x1 = Vector3::Zero();

 // Create handy typedefs and constants for vectors with N>3
 // VectorN and Z_Nx1, for N=1..9
 #define GTSAM_MAKE_VECTOR_DEFS(N)                \
   using Vector##N = Eigen::Matrix<double, N, 1>; \
-  static const Eigen::MatrixBase<Vector##N>::ConstantReturnType Z_##N##x1 = Vector##N::Zero();
+  static const decltype(Vector##N::Zero()) Z_##N##x1 = Vector##N::Zero();

 GTSAM_MAKE_VECTOR_DEFS(4)
 GTSAM_MAKE_VECTOR_DEFS(5)
diff --git a/gtsam/linear/iterative.h b/gtsam/linear/iterative.h
index 22f65b8de..20a0c936e 100644
--- a/gtsam/linear/iterative.h
+++ b/gtsam/linear/iterative.h
@@ -61,7 +61,7 @@ namespace gtsam {

     /** Apply operator A'*e */
     Vector operator^(const Vector& e) const {
-      return A_ ^ e;
+      return gtsam::operator^(A_, e);
     }

     /**
@@ -71,7 +71,7 @@ namespace gtsam {

     /** gradient of objective function 0.5*|Ax-b_|^2 at x = A_'*(Ax-b_) */
     Vector gradient(const Vector& x) const {
-      return A() ^ (A() * x - b());
+      return gtsam::operator^(A(), Vector(A() * x - b()));
     }

     /** Apply operator A */