diff --git a/CMakeLists.txt b/CMakeLists.txt
index d5300a609..02652ffc3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -207,7 +207,7 @@ ENDIF()
 NL_CONFIGURE_CHECKS()
 
 IF(WITH_STATIC_LIBXML2)
-  SET(LIBXML2_DEFINITIONS ${LIBXML2_DEFINITIONS} -DLIBXML_STATIC)
+  ADD_DEFINITIONS(-DLIBXML_STATIC)
 ENDIF()
 
 IF(WITH_LIBXML2_ICONV)