diff --git a/cmake/HandleEigen.cmake b/cmake/HandleEigen.cmake
index 707593889..becebafb9 100644
--- a/cmake/HandleEigen.cmake
+++ b/cmake/HandleEigen.cmake
@@ -13,12 +13,6 @@ if(GTSAM_USE_SYSTEM_EIGEN)
     # Since Eigen 3.3.0 a Eigen3Config.cmake is available so use it.
     find_package(Eigen3 CONFIG REQUIRED) # need to find again as REQUIRED
 
-    # The actual include directory (for BUILD cmake target interface):
-    # Note: EIGEN3_INCLUDE_DIR points to some random location on some eigen
-    # versions.  So here I use the target itself to get the proper include
-    # directory (it is generated by cmake, thus has the correct path)
-    get_target_property(GTSAM_EIGEN_INCLUDE_FOR_BUILD Eigen3::Eigen INTERFACE_INCLUDE_DIRECTORIES)
-
     # check if MKL is also enabled - can have one or the other, but not both!
     # Note: Eigen >= v3.2.5 includes our patches
     if(EIGEN_USE_MKL_ALL AND (EIGEN3_VERSION VERSION_LESS 3.2.5))
@@ -30,6 +24,8 @@ if(GTSAM_USE_SYSTEM_EIGEN)
     if(EIGEN_USE_MKL_ALL AND (EIGEN3_VERSION VERSION_EQUAL 3.3.4))
         message(FATAL_ERROR "MKL does not work with Eigen 3.3.4 because of a bug in Eigen. See http://eigen.tuxfamily.org/bz/show_bug.cgi?id=1527. Disable GTSAM_USE_SYSTEM_EIGEN to use GTSAM's copy of Eigen, disable GTSAM_WITH_EIGEN_MKL, or upgrade/patch your installation of Eigen.")
     endif()
+    
+    set(GTSAM_EIGEN_VERSION "${EIGEN3_VERSION}")
 else()
     # Use bundled Eigen include path.
     # Clear any variables set by FindEigen3
@@ -46,7 +42,7 @@ else()
 
     add_library(gtsam_eigen3 INTERFACE)
 
-    target_include_directories(gtsam_eigen3 INTERFACE
+    target_include_directories(gtsam_eigen3 SYSTEM INTERFACE
       $<BUILD_INTERFACE:${GTSAM_EIGEN_INCLUDE_FOR_BUILD}>
       $<INSTALL_INTERFACE:${GTSAM_EIGEN_INCLUDE_FOR_INSTALL}>
     )
@@ -56,11 +52,8 @@ else()
 
     list(APPEND GTSAM_EXPORTED_TARGETS gtsam_eigen3)
     set(GTSAM_EXPORTED_TARGETS "${GTSAM_EXPORTED_TARGETS}")
-endif()
-
-# Detect Eigen version:
-set(EIGEN_VER_H "${GTSAM_EIGEN_INCLUDE_FOR_BUILD}/Eigen/src/Core/util/Macros.h")
-if (EXISTS ${EIGEN_VER_H})
+    # Detect Eigen version:
+    set(EIGEN_VER_H "${GTSAM_EIGEN_INCLUDE_FOR_BUILD}/Eigen/src/Core/util/Macros.h")
     file(READ "${EIGEN_VER_H}" STR_EIGEN_VERSION)
 
     # Extract the Eigen version from the Macros.h file, lines "#define EIGEN_WORLD_VERSION  XX", etc...
@@ -75,11 +68,9 @@ if (EXISTS ${EIGEN_VER_H})
     string(REGEX MATCH "[0-9]+" GTSAM_EIGEN_VERSION_MINOR "${GTSAM_EIGEN_VERSION_MINOR}")
 
     set(GTSAM_EIGEN_VERSION "${GTSAM_EIGEN_VERSION_WORLD}.${GTSAM_EIGEN_VERSION_MAJOR}.${GTSAM_EIGEN_VERSION_MINOR}")
+endif()
 
-    message(STATUS "Found Eigen version: ${GTSAM_EIGEN_VERSION}")
-else()
-    message(WARNING "Cannot determine Eigen version, missing file: `${EIGEN_VER_H}`")
-endif ()
+message(STATUS "Found Eigen version: ${GTSAM_EIGEN_VERSION}")
 
 if (MSVC)
     if (GTSAM_SHARED_LIB)