diff --git a/st21nfc/hal/halcore.cc b/st21nfc/hal/halcore.cc
index 67ecbf9..13bc371 100644
--- a/st21nfc/hal/halcore.cc
+++ b/st21nfc/hal/halcore.cc
@@ -95,7 +95,7 @@
             usleep(1000 * (TX_DELAY - delta_time_ms));
         }
         rf_deactivate_delay = false;
-      } else if (data[0] == 0x00 && data[1] == 0x00) {
+      } else if (length > 1 && data[0] == 0x00 && data[1] == 0x00) {
         start_tx_data = HalGetTimestamp();
         rf_deactivate_delay = true;
       } else {