diff --git a/master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala b/master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala
index fa386e70e..bf9b5ba2d 100644
--- a/master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala
+++ b/master/src/main/scala/org/apache/celeborn/service/deploy/master/Master.scala
@@ -256,11 +256,11 @@ private[celeborn] class Master(
   }
 
   masterSource.addGauge(MasterSource.DEVICE_CELEBORN_TOTAL_CAPACITY) { () =>
-    statusSystem.workers.asScala.map(_.totalSpace()).sum
+    statusSystem.workers.asScala.toList.map(_.totalSpace()).sum
   }
 
   masterSource.addGauge(MasterSource.DEVICE_CELEBORN_FREE_CAPACITY) { () =>
-    statusSystem.workers.asScala.map(_.totalActualUsableSpace()).sum
+    statusSystem.workers.asScala.toList.map(_.totalActualUsableSpace()).sum
   }
 
   masterSource.addGauge(MasterSource.IS_ACTIVE_MASTER) { () => isMasterActive }