Improve -X error message.
diff --git a/Python/getopt.c b/Python/getopt.c
index acdd5d7..247600b 100644
--- a/Python/getopt.c
+++ b/Python/getopt.c
@@ -88,7 +88,7 @@
 
 	if (option == 'X') {
 		fprintf(stderr,
-			"-X is reserved for non-standard arguments\n");
+		  "-X is reserved for implementation-specific arguments\n");
 		return '_';
 	}