diff --git a/demo/CMakeLists.txt b/demo/CMakeLists.txt
--- a/demo/CMakeLists.txt
+++ b/demo/CMakeLists.txt
@@ -1,4 +1,8 @@
-INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR})
+INCLUDE_DIRECTORIES(
+  ${CMAKE_SOURCE_DIR}
+  ${CMAKE_BINARY_DIR}
+  ${GLPK_INCLUDE_DIR}
+)
 
 LINK_DIRECTORIES(${CMAKE_BINARY_DIR}/lemon)