diff --git a/cmake/externals/Sixense/CMakeLists.txt b/cmake/externals/Sixense/CMakeLists.txt
index 7991ccea1b..46341bd37b 100644
--- a/cmake/externals/Sixense/CMakeLists.txt
+++ b/cmake/externals/Sixense/CMakeLists.txt
@@ -1,3 +1,6 @@
+include(ExternalProject)
+include(SelectLibraryConfigurations)
+
 set(EXTERNAL_NAME Sixense)
 
 ExternalProject_Add(