diff --git a/armsrc/legicrfsim.c b/armsrc/legicrfsim.c
index 71c747115..1816a29ca 100644
--- a/armsrc/legicrfsim.c
+++ b/armsrc/legicrfsim.c
@@ -460,7 +460,7 @@ void LegicRfSimulate(uint8_t cardtype) {
 
   LED_A_ON();
   DbpString("Starting Legic emulator, press button to end");
-  while(!BUTTON_PRESS()) {
+  while (!BUTTON_PRESS() && !usb_poll_validate_length()) {
     WDT_HIT();
 
     // wait for carrier, restart after timeout