diff --git a/src/strings_type.h b/src/strings_type.h
--- a/src/strings_type.h
+++ b/src/strings_type.h
@@ -15,8 +15,8 @@
 /**
  * Numeric value that represents a string, independent of the selected language.
  */
-typedef uint16 StringID;
-static const StringID INVALID_STRING_ID = 0xFFFF; ///< Constant representing an invalid string
+typedef uint32 StringID;
+static const StringID INVALID_STRING_ID = 0xFFFF; ///< Constant representing an invalid string (16bit in case it is used in savegames)
 static const int MAX_CHAR_LENGTH        = 4;      ///< Max. length of UTF-8 encoded unicode character
 static const uint MAX_LANG              = 0x7F;   ///< Maximum number of languages supported by the game, and the NewGRF specs