diff --git a/converter/ibm4704_usb/matrix.c b/converter/ibm4704_usb/matrix.c
index 155df9c38..5b91d49f8 100644
--- a/converter/ibm4704_usb/matrix.c
+++ b/converter/ibm4704_usb/matrix.c
@@ -68,8 +68,9 @@ uint8_t matrix_cols(void)
 static void enable_break(void)
 {
     print("Enable break: ");
+    while (ibm4704_send(0xFC)) { _delay_ms(10); }
     // valid scancode: 00-79h
-    for (uint8_t code = 0; code < 0x7A; code++) {
+    for (uint8_t code = 0; code < 0x7F; code++) {
         while (ibm4704_send(0x80|code)) _delay_ms(10);
         _delay_ms(5);   // wait for response
         // No response(FF) when ok, FD when out of bound