diff --git a/oh-my-scheduler-server/src/main/java/com/github/kfcfans/oms/server/persistence/mongodb/GridFsManager.java b/oh-my-scheduler-server/src/main/java/com/github/kfcfans/oms/server/persistence/mongodb/GridFsManager.java
index 55ff19c4..29d11fe0 100644
--- a/oh-my-scheduler-server/src/main/java/com/github/kfcfans/oms/server/persistence/mongodb/GridFsManager.java
+++ b/oh-my-scheduler-server/src/main/java/com/github/kfcfans/oms/server/persistence/mongodb/GridFsManager.java
@@ -78,12 +78,13 @@ public class GridFsManager {
     public void download(File targetFile, String bucketName, String fileName) throws IOException {
         if (available()) {
             GridFSBucket bucket = getBucket(bucketName);
-            byte[] buffer = new byte[1024];
             try (GridFSDownloadStream gis = bucket.openDownloadStream(fileName);
                  BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(targetFile))
             ) {
-                while (gis.read(buffer) != -1) {
-                    bos.write(buffer);
+                byte[] buffer = new byte[1024];
+                int bytes = 0;
+                while ((bytes = gis.read(buffer)) != -1) {
+                    bos.write(buffer, 0, bytes);
                 }
                 bos.flush();
             }