diff --git a/samples/CMakeLists.txt b/samples/CMakeLists.txt
index 27266f28..1e7497a1 100644
--- a/samples/CMakeLists.txt
+++ b/samples/CMakeLists.txt
@@ -39,7 +39,7 @@ foreach(entry ${SAMPLES})
     set_target_properties(${target} PROPERTIES
       COMPILE_FLAGS ${EXTRA_COMPILE_FLAGS})
     list(APPEND APPLICATIONS ${target})
-    target_include_directories(${target} PRIVATE ${CMAKE_SOURCE_DIR}/src) # To find unused.h
+    target_include_directories(${target} PRIVATE ${PROJECT_SOURCE_DIR}/src) # To find enforce.hpp
     if ( NOT ${target} MATCHES ".*test.*")                                # don't install tests
         install( TARGETS ${target} RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
     endif()
@@ -54,20 +54,20 @@ endif()
 add_executable( getopt-test getopt-test.cpp ../app/getopt.cpp)
 list(APPEND APPLICATIONS getopt-test)
 target_include_directories(getopt-test PRIVATE 
-  ${CMAKE_SOURCE_DIR}/app
+  ${PROJECT_SOURCE_DIR}/app
 ) # To find getopt.hpp
 
 add_executable( metacopy metacopy.cpp metacopy.hpp ../app/getopt.cpp)
 list(APPEND APPLICATIONS metacopy)
 target_include_directories(metacopy PRIVATE 
-  ${CMAKE_SOURCE_DIR}/app
+  ${PROJECT_SOURCE_DIR}/app
 ) # To find getopt.hpp
 
 add_executable(          path-test  path-test.cpp ../app/getopt.cpp)
 list(APPEND APPLICATIONS path-test)
 set_target_properties(   path-test  PROPERTIES OUTPUT_NAME path-test )
 target_include_directories(path-test PRIVATE 
-  ${CMAKE_SOURCE_DIR}/app
+  ${PROJECT_SOURCE_DIR}/app
 ) # To find getopt.hpp
 
 install( TARGETS metacopy RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})