diff --git a/CMakeLists.txt b/CMakeLists.txt
index 63e2385..cc89ddd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,6 +5,7 @@ project(reflex2q3 CXX)
 set(OBJ_SRC "src/planes.cpp" "src/brushdef.cpp" "src/oopless-parser.cpp" "src/EntityConverter.cpp")
 add_library(objects OBJECT ${OBJ_SRC})
 
+
 add_executable(reflex2q3 src/main.cpp)
 add_executable(runtests test/catch.cpp)
 target_link_libraries(reflex2q3 objects)
@@ -14,10 +15,15 @@ set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED True)
 
 find_package(PkgConfig)
-pkg_check_modules(EIGEN REQUIRED eigen3)
+pkg_check_modules(EIGEN eigen3)
+if ( NOT EIGEN_FOUND) #use local
+	message ( WARNING "Install eigen3 using your package manager.  If using git eigen3 or a non-standard install location, ensure environment variable EIGEN3_INCLUDE_DIR is set." )
+	include_directories ( "$ENV{EIGEN3_INCLUDE_DIR}" )
+	find_package(Eigen3 REQUIRED NO_MODULE)
+endif ( NOT EIGEN_FOUND)
 
 include_directories(
-    ${EIGEN_INCLUDE_DIRS}
+    ${EIGEN_INCLUDE_DIRS} #set by pkg_check_modules
     "lib/Catch/single_include/catch2"
     "lib/cxxopts/include"
     "include"