diff --git a/include/timesync.h b/include/timesync.h
index 0cfe5571..f6d8fe80 100644
--- a/include/timesync.h
+++ b/include/timesync.h
@@ -11,6 +11,7 @@
 #define TIME_SYNC_TIMEOUT 120 // timeout seconds waiting for timeserver answer
 #define TIME_SYNC_TRIGGER 100 // time deviation in millisec triggering a sync
 #define TIME_SYNC_FRAME_LENGTH 0x06 // timeserver answer frame length
+#define TIME_SYNC_FIXUP 0 // calibration millisec to fixup processing time
 
 void send_timesync_req(void);
 int recv_timesync_ans(uint8_t buf[], uint8_t buf_len);
diff --git a/src/timesync.cpp b/src/timesync.cpp
index 514a5ea3..3e62a9fb 100644
--- a/src/timesync.cpp
+++ b/src/timesync.cpp
@@ -124,6 +124,8 @@ void process_timesync_req(void *taskparameter) {
   // calculate absolute time offset with millisecond precision using time base
   // of LMIC os, since we use LMIC's ostime_t txEnd as tx timestamp
   time_offset += milliseconds(osticks2ms(os_getTime()));
+  // apply calibration factor for processing time
+  time_offset += milliseconds(TIME_SYNC_FIXUP);
   // convert to seconds
   time_to_set = static_cast<time_t>(myClock_secTick(time_offset).count());
   // calculate fraction milliseconds
@@ -138,9 +140,9 @@ void process_timesync_req(void *taskparameter) {
         TIME_SYNC_TRIGGER) { // milliseconds threshold
 
       // wait until top of second
-      ESP_LOGD(TAG, "[%0.3f] waiting %d ms", millis() / 1000.0,
-               1000 - time_to_set_fraction_msec);
-      vTaskDelay(pdMS_TO_TICKS(1000 - time_to_set_fraction_msec));
+      uint16_t const wait_ms = 1000 - time_to_set_fraction_msec;
+      ESP_LOGD(TAG, "[%0.3f] waiting %d ms", millis() / 1000.0, wait_ms);
+      vTaskDelay(pdMS_TO_TICKS(wait_ms));
 
       // sync timer pps to top of second
       if (ppsIRQ) {