diff --git a/headers/os/support/Errors.h b/headers/os/support/Errors.h
index 350b7a6641..bd006305af 100644
--- a/headers/os/support/Errors.h
+++ b/headers/os/support/Errors.h
@@ -105,7 +105,8 @@ enum
 	B_LAUNCH_FAILED_APP_IN_TRASH,
 	B_LAUNCH_FAILED_NO_PREFERRED_APP,
 	B_LAUNCH_FAILED_FILES_APP_NOT_FOUND,
-	B_BAD_MIME_SNIFFER_RULE
+	B_BAD_MIME_SNIFFER_RULE,
+	B_NOT_A_MESSAGE
 };