diff --git a/CMakeLists.txt b/CMakeLists.txt
index 56e6129..679b95c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -150,7 +150,7 @@ IF(LIBTINS_ENABLE_ACK_TRACKER AND TINS_HAVE_CXX11)
     FIND_PACKAGE(Boost)
     IF (Boost_FOUND)
         MESSAGE(STATUS "Enabling TCP ACK tracking support.")
-        INCLUDE_DIRECTORIES(Boost_INCLUDE_DIRS)
+        INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})
         SET(TINS_HAVE_ACK_TRACKER ON)
     ELSE()
         MESSAGE(WARNING "Disabling ACK tracking support as boost.icl was not found")