extern "C" {\r
                #endif\r
 \r
+       /* Preprocessor Checks: */\r
+               #if !defined(__INCLUDE_FROM_CDC_DRIVER)\r
+                       #error Do not include this file directly. Include LUFA/Drivers/Class/CDC.h instead.\r
+               #endif\r
+\r
        /* Public Interface - May be used in end-application: */\r
                /* Type Defines: */\r
                        /** Class state structure. An instance of this structure should be made within the user application,\r
                        #define CDC_FOUND_NOTIFICATION_IN       (1 << 2)\r
 \r
                /* Function Prototypes: */\r
-                       #if defined(INCLUDE_FROM_CDC_CLASS_HOST_C)\r
+                       #if defined(__INCLUDE_FROM_CDC_CLASS_HOST_C)\r
                                static int CDC_Host_putchar(char c, FILE* Stream);\r
                                static int CDC_Host_getchar(FILE* Stream);\r
                                static int CDC_Host_getchar_Blocking(FILE* Stream);\r