diff --git a/core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala b/core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala
index 73fb0086b338c..8f64de0847ecd 100644
--- a/core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala
@@ -926,11 +926,12 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
    * UI lifecycle.
    */
   private def invalidateUI(appId: String, attemptId: Option[String]): Unit = {
-    synchronized {
-      activeUIs.get((appId, attemptId)).foreach { ui =>
-        ui.invalidate()
-        ui.ui.store.close()
-      }
+    val uiOption = synchronized {
+      activeUIs.get((appId, attemptId))
+    }
+    uiOption.foreach { ui =>
+      ui.invalidate()
+      ui.ui.store.close()
     }
   }