diff --git a/src/util/XMLUni.cpp b/src/util/XMLUni.cpp
index e69f1fff371409c80af11868983bb3931f57d946..382b5ce42e91a6457b2aa3eda2a12b3e65ef4176 100644
--- a/src/util/XMLUni.cpp
+++ b/src/util/XMLUni.cpp
@@ -817,3 +817,8 @@ const XMLCh XMLUni::fgZeroString[] =
     chDigit_0, chNull
 };
 
+const XMLCh XMLUni::fgNullString[] =
+{
+    chLatin_n, chLatin_u, chLatin_l, chLatin_l, chNull
+};
+
diff --git a/src/util/XMLUni.hpp b/src/util/XMLUni.hpp
index 867dfa363344ea468ed6558ddd6c290f3846a03d..c2ae30aed9887217bbb86af6db25c2d0cb8543d0 100644
--- a/src/util/XMLUni.hpp
+++ b/src/util/XMLUni.hpp
@@ -214,6 +214,7 @@ public :
     static const XMLCh fgNaNString[];
     static const XMLCh fgEString[];
     static const XMLCh fgZeroString[];
+    static const XMLCh fgNullString[];
 
 };