diff --git a/src/paxcounter.conf b/src/paxcounter.conf
index 30dcedc0..9dffe04e 100644
--- a/src/paxcounter.conf
+++ b/src/paxcounter.conf
@@ -94,6 +94,7 @@
 #define BMEPORT                         7       // BME680 sensor
 #define BATTPORT                        8       // battery voltage
 #define TIMEPORT                        9       // time query
+#define TIMEDIFFPORT                    13      // time adjust diff
 #define TIMEANSWERPORT_MIN              0xA0    // time answer, start of port range
 #define TIMEANSWERPORT_MAX              0xDF    // time answer, end of port range
 #define SENSOR1PORT                     10      // user sensor #1