diff --git a/src/constants.cpp b/src/constants.cpp
index 494428a2..cc1005bf 100644
--- a/src/constants.cpp
+++ b/src/constants.cpp
@@ -42,6 +42,7 @@ namespace mediaTypes
 	const string::value_type* const TEXT_RICHTEXT = "richtext";
 	const string::value_type* const TEXT_ENRICHED = "enriched";
 	const string::value_type* const TEXT_RFC822_HEADERS = "rfc822-headers";  // RFC-1892
+	const string::value_type* const TEXT_DIRECTORY = "directory";  // RFC-2426
 
 	const string::value_type* const MULTIPART_MIXED = "mixed";
 	const string::value_type* const MULTIPART_RELATED = "related";
diff --git a/vmime/constants.hpp b/vmime/constants.hpp
index 90a9c699..463c2145 100644
--- a/vmime/constants.hpp
+++ b/vmime/constants.hpp
@@ -53,6 +53,7 @@ namespace vmime
 		extern const string::value_type* const TEXT_RICHTEXT;
 		extern const string::value_type* const TEXT_ENRICHED;
 		extern const string::value_type* const TEXT_RFC822_HEADERS;  // RFC-1892
+		extern const string::value_type* const TEXT_DIRECTORY;  // RFC-2426
 
 		extern const string::value_type* const MULTIPART_MIXED;
 		extern const string::value_type* const MULTIPART_RELATED;