diff --git a/app/src/main/java/info/nightscout/androidaps/plugins/source/DexcomPlugin.kt b/app/src/main/java/info/nightscout/androidaps/plugins/source/DexcomPlugin.kt
index 5bef08a3f8..0255209c5e 100644
--- a/app/src/main/java/info/nightscout/androidaps/plugins/source/DexcomPlugin.kt
+++ b/app/src/main/java/info/nightscout/androidaps/plugins/source/DexcomPlugin.kt
@@ -149,11 +149,15 @@ class DexcomPlugin @Inject constructor(
                             sourceSensor = sourceSensor
                         )
                 }
-                val sensorStartTime = if (sp.getBoolean(R.string.key_dexcom_lognssensorchange, false) && bundle.containsKey("sensorInsertionTime")) {
+                var sensorStartTime = if (sp.getBoolean(R.string.key_dexcom_lognssensorchange, false) && bundle.containsKey("sensorInsertionTime")) {
                     bundle.getLong("sensorInsertionTime", 0) * 1000
                 } else {
                     null
                 }
+                // check start time validity
+                sensorStartTime?.let {
+                    if (abs(it - now) > T.months(1).msecs() || it > now) sensorStartTime = null
+                }
                 repository.runTransactionForResult(CgmSourceTransaction(glucoseValues, calibrations, sensorStartTime))
                     .doOnError {
                         aapsLogger.error(LTag.DATABASE, "Error while saving values from Dexcom App", it)