diff --git a/library/core-utils/src/main/java/im/vector/lib/core/utils/timer/CountUpTimer.kt b/library/core-utils/src/main/java/im/vector/lib/core/utils/timer/CountUpTimer.kt
index debb1d0f4b..0be20675af 100644
--- a/library/core-utils/src/main/java/im/vector/lib/core/utils/timer/CountUpTimer.kt
+++ b/library/core-utils/src/main/java/im/vector/lib/core/utils/timer/CountUpTimer.kt
@@ -34,7 +34,7 @@ class CountUpTimer(initialTime: Long = 0L, private val intervalInMs: Long = 1_00
     private val resumed: AtomicBoolean = AtomicBoolean(false)
 
     private val clock: Clock = DefaultClock()
-    private var lastTime: AtomicLong = AtomicLong()
+    private val lastTime: AtomicLong = AtomicLong()
     private val elapsedTime: AtomicLong = AtomicLong(initialTime)
 
     init {