diff --git a/cmake/modules/FindEigen3.cmake b/cmake/modules/FindEigen3.cmake
index fe82bb9f..e33a2678 100644
--- a/cmake/modules/FindEigen3.cmake
+++ b/cmake/modules/FindEigen3.cmake
@@ -49,7 +49,18 @@ if(NOT Eigen3_FIND_VERSION)
 endif()
 
 macro(_eigen3_check_version)
-  file(READ "${EIGEN3_INCLUDE_DIR}/Eigen/src/Core/util/Macros.h" _eigen3_version_header)
+  # Try the Eigen 5.x location first
+  if(EXISTS "${EIGEN3_INCLUDE_DIR}/Eigen/Version")
+    file(READ "${EIGEN3_INCLUDE_DIR}/Eigen/Version" _eigen3_version_header)
+  # Fall back to Eigen 3.x location
+  elseif(EXISTS "${EIGEN3_INCLUDE_DIR}/Eigen/src/Core/util/Macros.h")
+    file(READ "${EIGEN3_INCLUDE_DIR}/Eigen/src/Core/util/Macros.h" _eigen3_version_header)
+  else()
+    # Could not locate any known Eigen version header; mark version as not OK and return.
+    set(EIGEN3_VERSION_OK FALSE)
+    message(STATUS "Could not find Eigen version header under ${EIGEN3_INCLUDE_DIR}")
+    return()
+  endif()
 
   string(REGEX MATCH "define[ \t]+EIGEN_WORLD_VERSION[ \t]+([0-9]+)" _eigen3_world_version_match "${_eigen3_version_header}")
   set(EIGEN3_WORLD_VERSION "${CMAKE_MATCH_1}")
diff --git a/cmake/modules/int_checkboost.cmake b/cmake/modules/int_checkboost.cmake
index 016a788c..2101efe2 100644
--- a/cmake/modules/int_checkboost.cmake
+++ b/cmake/modules/int_checkboost.cmake
@@ -4,7 +4,31 @@ cmake_policy(SET CMP0075 NEW)  # support CMAKE_REQUIRED_LIBRARIES
 include(CMakePushCheckState)
 
 cmake_push_check_state()
-list(APPEND CMAKE_REQUIRED_LIBRARIES Boost::headers)
+if (NOT TARGET Boost::headers)
+    message(FATAL_ERROR "int_checkboost.cmake: can only invoke if Boost::headers is already available")
+endif()
+# can only link against system or IMPORTED target here
+get_target_property(BOOST_HEADERS_IS_IMPORTED Boost::headers IMPORTED)
+if (BOOST_HEADERS_IS_IMPORTED)
+    list(APPEND CMAKE_REQUIRED_LIBRARIES Boost::headers)
+else()  # if Boost::headers is not IMPORTED, it was built within this project, extract its properties
+    # Collect include directories from Boost::headers and Boost::preprocessor (for modularized Boost)
+    set(_boost_targets_to_check Boost::headers)
+    if (TARGET Boost::preprocessor)
+        list(APPEND _boost_targets_to_check Boost::preprocessor)
+    endif()
+    foreach(_boost_target IN LISTS _boost_targets_to_check)
+        get_target_property(_interface_include_dirs ${_boost_target} INTERFACE_INCLUDE_DIRECTORIES)
+        if (_interface_include_dirs)
+            # Extract paths from $<BUILD_INTERFACE:...> generator expressions
+            string(REGEX MATCHALL "\\$<BUILD_INTERFACE:([^>]+)>" _build_interface_matches "${_interface_include_dirs}")
+            foreach(_match IN LISTS _build_interface_matches)
+                string(REGEX REPLACE "\\$<BUILD_INTERFACE:([^>]+)>" "\\1" _include_dir "${_match}")
+                list(APPEND CMAKE_REQUIRED_INCLUDES "${_include_dir}")
+            endforeach()
+        endif()
+    endforeach()
+endif()
 #list(APPEND CMAKE_REQUIRED_FLAGS "-std=c++11")  # set CMAKE_CXX_STANDARD and 0067 NEW ?
 
 check_cxx_source_compiles("
diff --git a/doc/wiki b/doc/wiki
index d0057dd3..6ce8b99e 160000
--- a/doc/wiki
+++ b/doc/wiki
@@ -1 +1 @@
-Subproject commit d0057dd3e920b01eb969e35656925d6d1cf8c80f
+Subproject commit 6ce8b99e384658e973097ce1339b59d2acb64721
diff --git a/export/CMakeLists.txt.export b/export/CMakeLists.txt.export
index 3c28edb4..45fb1a78 100644
--- a/export/CMakeLists.txt.export
+++ b/export/CMakeLists.txt.export
@@ -172,7 +172,7 @@ find_package(Eigen3 MODULE)
 if (TARGET Eigen3::Eigen)
     set(LIBINT_HAS_EIGEN 1)
 endif()
-if (LIBINT2_REQUIRE_CXX_API AND NOT ${LIBINT_HAS_EIGEN})
+if (LIBINT2_REQUIRE_CXX_API AND NOT LIBINT_HAS_EIGEN)
     message(FATAL_ERROR "C++ API cannot be built without Eigen3; configure (via CMake) and install Eigen3 and add the install prefix to CMAKE_PREFIX_PATH, or add -D LIBINT2_REQUIRE_CXX_API=OFF to the CMake command line if the C++ API is not required")
 endif()