diff --git a/src/rtctime.cpp b/src/rtctime.cpp
index 7bbb4844..0de8e176 100644
--- a/src/rtctime.cpp
+++ b/src/rtctime.cpp
@@ -65,7 +65,13 @@ time_t get_rtctime(uint16_t *msec) {
 
 // if we have a RTC pulse, we calculate msec
 #ifdef RTC_INT
-  *msec = lastRTCpulse % 1000;
+  uint16_t ppsDiff = millis() - lastRTCpulse;
+  if (ppsDiff < 1000)
+    *msec = ppsDiff;
+  else {
+    ESP_LOGD(TAG, "no pulse from RTC");
+    return 0;
+  }
 #endif
 
   return t;
diff --git a/src/timekeeper.cpp b/src/timekeeper.cpp
index 97c63064..ee0a4ed1 100644
--- a/src/timekeeper.cpp
+++ b/src/timekeeper.cpp
@@ -203,8 +203,10 @@ void timepulse_init(void) {
 #endif
 
   // get time if we don't have one
-  if (timeSource != _set)
+  if (timeSource != _set) {
+    delay(1000);      // wait for first PPS time stamp to arrive
     setTimeSyncIRQ(); // init systime by RTC or GPS or LORA
+  }
 
   // start cyclic time sync
   timesyncer.attach(TIME_SYNC_INTERVAL * 60, setTimeSyncIRQ);