diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1fed950..e4512b4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,7 +38,7 @@ set(CMAKE_CXX_FLAGS "-Wall -Werror -Wpedantic")
 
 
 if (UNIT_TESTING)
-
+    add_definitions(-DUNIT_TESTING)
     if(DEFINED ENV{CPPUTEST_HOME})
         message(STATUS "Using CppUTest home: $ENV{CPPUTEST_HOME}")
         set(CPPUTEST_INCLUDE_DIRS $ENV{CPPUTEST_HOME}/include)