diff --git a/states.h b/states.h
--- a/states.h
+++ b/states.h
@@ -8,6 +8,7 @@ typedef struct {
     uint8_t state;
     int32_t setpoint;
     uint8_t pid_enabled;
+    uint8_t tc_errno;
 } therm_status_t;
 
 typedef struct {