diff --git a/cubesatsim/cubesatsim.h b/cubesatsim/cubesatsim.h
index 21abed8a..e08dcfff 100644
--- a/cubesatsim/cubesatsim.h
+++ b/cubesatsim/cubesatsim.h
@@ -111,6 +111,8 @@
 #define PROMPT_QUERY 5
 
 volatile int prompt = false;
+char serial_string[128];
+
 //#define WAV_DATA_LENGTH (50000 * 8)
 
 uint32_t tx_freq_hz = 434900000 + FREQUENCY_OFFSET;