diff --git a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/counters/CounterSnapshotsTree.java b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/counters/CounterSnapshotsTree.java
index 0f7d990ef931..707a9794296a 100644
--- a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/counters/CounterSnapshotsTree.java
+++ b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/counters/CounterSnapshotsTree.java
@@ -121,7 +121,9 @@ public boolean equals(Object o)
     }
     CounterSnapshotsTree that = (CounterSnapshotsTree) o;
     synchronized (snapshotsMap) {
-      return Objects.equals(snapshotsMap, that.snapshotsMap);
+      synchronized (that.snapshotsMap) {
+        return Objects.equals(snapshotsMap, that.snapshotsMap);
+      }
     }
   }