diff --git a/spark-extension/src/main/scala/org/apache/spark/sql/blaze/memory/SpillBuf.scala b/spark-extension/src/main/scala/org/apache/spark/sql/blaze/memory/SpillBuf.scala
index e3aa3262e..597c37112 100644
--- a/spark-extension/src/main/scala/org/apache/spark/sql/blaze/memory/SpillBuf.scala
+++ b/spark-extension/src/main/scala/org/apache/spark/sql/blaze/memory/SpillBuf.scala
@@ -108,6 +108,7 @@ class FileBasedSpillBuf(
     with Logging {
 
   private var readPosition: Long = 0
+  private var closedFileDiskUsage: Long = 0
 
   override def write(buf: ByteBuffer): Unit = {
     val startTimeNs = System.nanoTime()
@@ -126,12 +127,21 @@ class FileBasedSpillBuf(
   }
 
   override val memUsed: Long = 0
-  override def diskUsed: Long = fileChannel.size()
+  override def diskUsed: Long = {
+    if (fileChannel.isOpen) {
+      fileChannel.size()
+    } else {
+      closedFileDiskUsage
+    }
+  }
   override def diskIOTime: Long = diskIOTimeNs
   override def size: Long = numWrittenBytes
 
   override def release(): Unit = {
-    fileChannel.close()
+    if (fileChannel.isOpen) {
+      closedFileDiskUsage = fileChannel.size()
+      fileChannel.close()
+    }
     if (!file.delete()) {
       logWarning(s"Was unable to delete spill file: ${file.getAbsolutePath}")
     }