diff --git a/CGAL_ipelets/demo/CGAL_ipelets/CMakeLists.txt b/CGAL_ipelets/demo/CGAL_ipelets/CMakeLists.txt
index cad2c3889dc..83f66e52253 100644
--- a/CGAL_ipelets/demo/CGAL_ipelets/CMakeLists.txt
+++ b/CGAL_ipelets/demo/CGAL_ipelets/CMakeLists.txt
@@ -25,6 +25,14 @@ find_package(CGAL QUIET COMPONENTS Core)
 if ( CGAL_FOUND )
   include( ${CGAL_USE_FILE} )
 
+  find_package(Eigen3 3.1.0) #(requires 3.1.0 or greater)
+  if (EIGEN3_FOUND)
+    include( ${EIGEN3_USE_FILE} )
+  else()
+    message(STATUS "NOTICE: This project requires the Eigen library, and will not be compiled.")
+    return()
+  endif()
+
   find_package(IPE 6)
 
   if ( IPE_FOUND )
diff --git a/GraphicsView/demo/Polygon/CMakeLists.txt b/GraphicsView/demo/Polygon/CMakeLists.txt
index ed26300f92c..f84197f4cc1 100644
--- a/GraphicsView/demo/Polygon/CMakeLists.txt
+++ b/GraphicsView/demo/Polygon/CMakeLists.txt
@@ -13,6 +13,14 @@ find_package(CGAL COMPONENTS Qt5 Core)
 
 include(${CGAL_USE_FILE})
 
+find_package(Eigen3 3.1.0) #(requires 3.1.0 or greater)
+if (EIGEN3_FOUND)
+  include( ${EIGEN3_USE_FILE} )
+else()
+  message(STATUS "NOTICE: This project requires the Eigen library, and will not be compiled.")
+  return()
+endif()
+
 find_package(Qt5 QUIET COMPONENTS Xml Script OpenGL Svg)
 
 include_directories (BEFORE ../../include)
diff --git a/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt b/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt
index c7f68b6629c..478cc49ca88 100644
--- a/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt
+++ b/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt
@@ -20,6 +20,14 @@ include_directories( ./ )
 find_package(CGAL COMPONENTS Qt5)
 include( ${CGAL_USE_FILE} )
 
+find_package(Eigen3 3.1.0) #(requires 3.1.0 or greater)
+if (EIGEN3_FOUND)
+  include( ${EIGEN3_USE_FILE} )
+else()
+  message(STATUS "NOTICE: This project requires the Eigen library, and will not be compiled.")
+  return()
+endif()
+
 # Find Qt5 itself
 find_package(Qt5 QUIET COMPONENTS Xml Script OpenGL)