diff --git a/Modules/CheckTypeSize.cmake b/Modules/CheckTypeSize.cmake
index be7615416..c4163cc1a 100644
--- a/Modules/CheckTypeSize.cmake
+++ b/Modules/CheckTypeSize.cmake
@@ -19,6 +19,7 @@ MACRO(CHECK_TYPE_SIZE TYPE VARIABLE)
       ENDIF("${def}")
     ENDFOREACH(def)
     SET(CHECK_TYPE_SIZE_PREINCLUDE)
+    SET(CHECK_TYPE_SIZE_PREMAIN)
     FOREACH(def ${CMAKE_EXTRA_INCLUDE_FILES})
       SET(CHECK_TYPE_SIZE_PREMAIN "${CHECK_TYPE_SIZE_PREMAIN}#include \"${def}\"\n")
     ENDFOREACH(def)