diff --git a/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedImpressionData.kt b/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedImpressionData.kt
index e166fa2e9..a8947c052 100644
--- a/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedImpressionData.kt
+++ b/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedImpressionData.kt
@@ -9,7 +9,7 @@ data class EmbeddedImpressionData(
     val placementId: Long,
     var displayCount: Int = 0,
     var duration: Float = 0.0f,
-    var start: Date? = null
+    @Volatile var start: Date? = null
 ) {
     constructor(
         messageId: String,
diff --git a/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedSessionManager.kt b/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedSessionManager.kt
index cbedfe4fd..b1271111c 100644
--- a/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedSessionManager.kt
+++ b/iterableapi/src/main/java/com/iterable/iterableapi/EmbeddedSessionManager.kt
@@ -108,12 +108,15 @@ public class EmbeddedSessionManager {
     }
 
     private fun updateDisplayCountAndDuration(impressionData: EmbeddedImpressionData): EmbeddedImpressionData {
-        if (impressionData.start != null) {
-            impressionData.displayCount = impressionData.displayCount.plus(1)
-            impressionData.duration =
-                impressionData.duration.plus((Date().time - impressionData.start!!.time) / 1000.0)
-                    .toFloat()
-            impressionData.start = null
+        synchronized(impressionData) {
+            val start = impressionData.start
+            if (start != null) {
+                impressionData.displayCount = impressionData.displayCount.plus(1)
+                impressionData.duration =
+                    impressionData.duration.plus((Date().time - start.time) / 1000.0)
+                        .toFloat()
+                impressionData.start = null
+            }
         }
         return impressionData
     }