diff --git a/Modules/main.c b/Modules/main.c
index 0cd879d..21cb487 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -40,7 +40,7 @@
 static int  orig_argc;
 
 /* command line options */
-#define BASE_OPTS "3Bc:dEhim:OQ:StuUvVW:xX?"
+#define BASE_OPTS "3bBc:dEhim:OQ:StuUvVW:xX?"
 
 #ifndef RISCOS
 #define PROGRAM_OPTS BASE_OPTS
@@ -296,6 +296,9 @@
 		}
 
 		switch (c) {
+		case 'b':
+			Py_BytesWarningFlag++;
+			break;
 
 		case 'd':
 			Py_DebugFlag++;