diff --git a/app/src/main/kotlin/com/simplemobiletools/flashlight/helpers/SleepTimer.kt b/app/src/main/kotlin/com/simplemobiletools/flashlight/helpers/SleepTimer.kt
index ebc6330..44e2bd9 100644
--- a/app/src/main/kotlin/com/simplemobiletools/flashlight/helpers/SleepTimer.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/flashlight/helpers/SleepTimer.kt
@@ -20,7 +20,7 @@ object SleepTimer {
     val timeLeft = _timeLeft.asSharedFlow()
     private val scope = CoroutineScope(Dispatchers.Default)
 
-    fun cancel() {
+    fun cancel() = synchronized(this@SleepTimer) {
         sleepTimer?.cancel()
         sleepTimer = null
     }