diff --git a/BasisProject.cmake b/BasisProject.cmake
index 9de2a6c..61f543c 100644
--- a/BasisProject.cmake
+++ b/BasisProject.cmake
@@ -39,6 +39,7 @@ basis_project (
     #<dependency>
   OPTIONAL_DEPENDS
     TBB{tbb}
+    ITK
     #<optional-dependency>
   TOOLS_DEPENDS
     MIRTK{IO}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index e1a18e4..674a8a1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,5 +26,5 @@ endif ()
 
 mirtk_configure_module()
 
-SUBDIRS(ThirdParty/ANTs)
-INCLUDE(Atlases.cmake)
+add_subdirectory(ThirdParty/ANTs)
+include(Atlases.cmake)
diff --git a/ThirdParty/ANTs/CMakeLists.txt b/ThirdParty/ANTs/CMakeLists.txt
index db43a6e..0bf20f8 100755
--- a/ThirdParty/ANTs/CMakeLists.txt
+++ b/ThirdParty/ANTs/CMakeLists.txt
@@ -9,6 +9,9 @@ PROJECT( N4 )
 IF(NOT ITK_DIR)
   INCLUDE(External_ITK.cmake)
   SET(External_ITK 1)
+  MESSAGE(STATUS "Build ITK as external project for build of DrawEM::N4")
+ELSE()
+  MESSAGE(STATUS "Use system-wide ITK installation for build of DrawEM::N4")
 ENDIF()
 
 # Set up ITK