diff --git a/CI/Windows.bat b/CI/Windows.bat
index 616dcf27..acb1e2d2 100644
--- a/CI/Windows.bat
+++ b/CI/Windows.bat
@@ -107,7 +107,7 @@ IF EXIST %QT_INSTALL_PATH%\ (
 )
 
 
-"C:\Program Files\CMake\bin\cmake.exe" -DGTEST_ROOT="%LIBPATH%\%ARCHITECTURE%\%GTESTVERSION%" -G "%GENERATOR%"  -DCMAKE_BUILD_TYPE=Release -DBUILD_APPS=%APPS% -DOPENMESH_BUILD_UNIT_TESTS=TRUE -DCMAKE_WINDOWS_LIBS_DIR="e:\libs" -DOPENMESH_BUILD_SHARED=%SHARED% %CMAKE_CONFIGURATION% ..
+"C:\Program Files\CMake\bin\cmake.exe" -DGTEST_ROOT="%LIBPATH%\%ARCHITECTURE%\%GTESTVERSION%" -G "%GENERATOR%"  -DCMAKE_BUILD_TYPE=Release -DBUILD_APPS=%APPS% -DOPENMESH_BUILD_UNIT_TESTS=TRUE -DCMAKE_WINDOWS_LIBS_DIR="e:\libs" -DEigen3_DIR="e:\libs\general\Eigen3.3.9\share\eigen3\cmake"  -DOPENMESH_BUILD_SHARED=%SHARED% %CMAKE_CONFIGURATION% ..
 
 %VS_PATH% /Build "Release" OpenMesh.sln /Project "ALL_BUILD"
 
@@ -129,7 +129,7 @@ mkdir build-debug
 
 cd build-debug
 
-"C:\Program Files\CMake\bin\cmake.exe" -DGTEST_ROOT="%LIBPATH%\%ARCHITECTURE%\%GTESTVERSION%" -G "%GENERATOR%" -DOPENMESH_BUILD_UNIT_TESTS=TRUE  -DCMAKE_BUILD_TYPE=Debug -DOPENMESH_BUILD_SHARED=%SHARED% -DBUILD_APPS=%APPS% %CMAKE_CONFIGURATION% ..
+"C:\Program Files\CMake\bin\cmake.exe" -DGTEST_ROOT="%LIBPATH%\%ARCHITECTURE%\%GTESTVERSION%" -G "%GENERATOR%" -DOPENMESH_BUILD_UNIT_TESTS=TRUE -DEigen3_DIR="e:\libs\general\Eigen3.3.9\share\eigen3\cmake" -DCMAKE_BUILD_TYPE=Debug -DOPENMESH_BUILD_SHARED=%SHARED% -DBUILD_APPS=%APPS% %CMAKE_CONFIGURATION% ..
 
 %VS_PATH% /Build "Debug" OpenMesh.sln /Project "ALL_BUILD"
 
diff --git a/src/Unittests/CMakeLists.txt b/src/Unittests/CMakeLists.txt
index b52434e4..22595feb 100644
--- a/src/Unittests/CMakeLists.txt
+++ b/src/Unittests/CMakeLists.txt
@@ -30,6 +30,8 @@ if ( OPENMESH_BUILD_UNIT_TESTS )
     if (TARGET Eigen3::Eigen)
       add_definitions( -DENABLE_EIGEN3_TEST ) 
       link_libraries(Eigen3::Eigen)
+    else()
+      message(WARNING "Eigen3 not found! This will skip the Eigen3 Unittests. You can point cmake to Eigen3 by setting Eigen3_DIR to the cmake files of Eigen3")
     endif()
 
     if ( CMAKE_GENERATOR MATCHES "^Visual Studio 11.*" )