diff --git a/testing/CMakeLists.txt b/testing/CMakeLists.txt
index b7abf45..5afd526 100644
--- a/testing/CMakeLists.txt
+++ b/testing/CMakeLists.txt
@@ -2,6 +2,8 @@
 
 include(CTest)
 
+include_directories(${CMAKE_SOURCE_DIR}/heat)
+
 function(make_test test_name)
   add_test(NAME ${test_name} COMMAND ${test_name})
   add_executable(${test_name} ${test_name}.c)