diff --git a/app/src/main/java/org/blitzortung/android/app/Main.kt b/app/src/main/java/org/blitzortung/android/app/Main.kt
index 1b4b363d..d39b1c35 100644
--- a/app/src/main/java/org/blitzortung/android/app/Main.kt
+++ b/app/src/main/java/org/blitzortung/android/app/Main.kt
@@ -142,10 +142,16 @@ class Main : FragmentActivity(), OnSharedPreferenceChangeListener {
                 if (!event.failed && event.sequenceNumber != null) {
                     val updatedSequenceNumber =
                         if (isAtLeast(24)) {
-                        currentSequenceNumber.updateAndGet { previousSequenceNumber ->
-                            if (previousSequenceNumber < event.sequenceNumber) event.sequenceNumber else previousSequenceNumber
-                        }} else {
-                            if (currentSequenceNumber.get() < event.sequenceNumber) event.sequenceNumber else currentSequenceNumber.get()
+                            currentSequenceNumber.updateAndGet { previousSequenceNumber ->
+                                if (previousSequenceNumber < event.sequenceNumber) event.sequenceNumber else previousSequenceNumber
+                            }
+                        } else {
+                            synchronized(currentSequenceNumber) {
+                                val previousSequenceNumber = currentSequenceNumber.get()
+                                val updated = if (previousSequenceNumber < event.sequenceNumber) event.sequenceNumber else previousSequenceNumber
+                                currentSequenceNumber.set(updated)
+                                updated
+                            }
                         }
                     if (updatedSequenceNumber == event.sequenceNumber) {
                         currentResult = event