diff --git a/src/uas/UAS.cc b/src/uas/UAS.cc
index dbb342518627aec9fab71d109b6b0e99d4c303e7..1ebc9127a571133c1f3684a37cac59e78a269157 100644
--- a/src/uas/UAS.cc
+++ b/src/uas/UAS.cc
@@ -104,7 +104,9 @@ UAS::UAS(MAVLinkProtocol* protocol, int id) : UASInterface(),
     nedPosGlobalOffset(0,0,0),
     nedAttGlobalOffset(0,0,0),
     connectionLost(false),
-    lastVoltageWarning(0)
+    lastVoltageWarning(0),
+    lastNonNullTime(0),
+    onboardTimeOffsetInvalidCount(0)
 
 {
     for (unsigned int i = 0; i<255;++i)
@@ -1533,6 +1535,26 @@ quint64 UAS::getUnixTimeFromMs(quint64 time)
 */
 quint64 UAS::getUnixTime(quint64 time)
 {
+    // Check if the offset estimation likely went wrong
+    // and we're talking to a new instance / the system
+    // has rebooted. Only reset if this is consistent.
+    if (time != 0 && lastNonNullTime > time)
+    {
+        onboardTimeOffsetInvalidCount++;
+    }
+    else if (lastNonNullTime < time)
+    {
+        onboardTimeOffsetInvalidCount = 0;
+    }
+
+    // Reset onboard time offset estimation, since it seems to be really off
+    if (onboardTimeOffsetInvalidCount > 20)
+    {
+        onboardTimeOffset = 0;
+        onboardTimeOffsetInvalidCount = 0;
+    }
+
+
     quint64 ret = 0;
     if (attitudeStamped)
     {
diff --git a/src/uas/UAS.h b/src/uas/UAS.h
index f5fe0df4e87bfee134306df99769aa794f4cebcc..a2769aad92f63f7095410f766f35ad8a7ebffa36 100644
--- a/src/uas/UAS.h
+++ b/src/uas/UAS.h
@@ -674,6 +674,8 @@ protected:
     bool connectionLost; ///< Flag indicates a timed out connection
     quint64 connectionLossTime; ///< Time the connection was interrupted
     quint64 lastVoltageWarning; ///< Time at which the last voltage warning occured
+    quint64 lastNonNullTime;    ///< The last timestamp from the MAV that was not null
+    unsigned int onboardTimeOffsetInvalidCount;     ///< Count when the offboard time offset estimation seemed wrong
 
 protected slots:
     /** @brief Write settings to disk */