diff --git a/src/base.cpp b/src/base.cpp
index 79ad0655..5927e74e 100644
--- a/src/base.cpp
+++ b/src/base.cpp
@@ -62,6 +62,10 @@ const string NULL_STRING;
   */
 const text NULL_TEXT;
 
+/** "Null" (empty) word.
+  */
+const word NULL_WORD;
+
 
 /** Return the library name (eg. "libvmime").
   *
diff --git a/vmime/base.hpp b/vmime/base.hpp
index 175bfdd9..8177a641 100644
--- a/vmime/base.hpp
+++ b/vmime/base.hpp
@@ -37,6 +37,7 @@
 namespace vmime
 {
 	class text;
+	class word;
 	class charset;
 
 
@@ -47,6 +48,7 @@ namespace vmime
 #endif
 
 	extern const text NULL_TEXT;
+	extern const word NULL_WORD;
 
 
 	//
diff --git a/vmime/defaultAttachment.hpp b/vmime/defaultAttachment.hpp
index f5a1a5b6..d938cb46 100644
--- a/vmime/defaultAttachment.hpp
+++ b/vmime/defaultAttachment.hpp
@@ -41,8 +41,8 @@ protected:
 
 public:
 
-	defaultAttachment(ref <contentHandler> data, const encoding& enc, const mediaType& type, const text& desc = NULL_TEXT, const word& name = NULL_TEXT);
-	defaultAttachment(ref <contentHandler> data, const mediaType& type, const text& desc = NULL_TEXT, const word& name = NULL_TEXT);
+	defaultAttachment(ref <contentHandler> data, const encoding& enc, const mediaType& type, const text& desc = NULL_TEXT, const word& name = NULL_WORD);
+	defaultAttachment(ref <contentHandler> data, const mediaType& type, const text& desc = NULL_TEXT, const word& name = NULL_WORD);
 	defaultAttachment(const defaultAttachment& attach);
 
 	~defaultAttachment();