diff --git a/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/ExternalCheckpointManagerSuite.scala b/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/ExternalCheckpointManagerSuite.scala
index e6835158d..729bd9c77 100755
--- a/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/ExternalCheckpointManagerSuite.scala
+++ b/jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/ExternalCheckpointManagerSuite.scala
@@ -50,13 +50,13 @@ class ExternalCheckpointManagerSuite extends AnyFunSuite with TmpFolderPerSuite
     manager.updateCheckpoint(model2._booster.booster)
     var files = FileSystem.get(sc.hadoopConfiguration).listStatus(new Path(tmpPath))
     assert(files.length == 1)
-    assert(files.head.getPath.getName == "1.model")
+    assert(files.head.getPath.getName == "1.ubj")
     assert(manager.loadCheckpointAsScalaBooster().getNumBoostedRound == 2)
 
     manager.updateCheckpoint(model4._booster)
     files = FileSystem.get(sc.hadoopConfiguration).listStatus(new Path(tmpPath))
     assert(files.length == 1)
-    assert(files.head.getPath.getName == "3.model")
+    assert(files.head.getPath.getName == "3.ubj")
     assert(manager.loadCheckpointAsScalaBooster().getNumBoostedRound == 4)
   }
 
@@ -66,10 +66,10 @@ class ExternalCheckpointManagerSuite extends AnyFunSuite with TmpFolderPerSuite
     val manager = new ExternalCheckpointManager(tmpPath, FileSystem.get(sc.hadoopConfiguration))
     manager.updateCheckpoint(model4._booster)
     manager.cleanUpHigherVersions(3)
-    assert(new File(s"$tmpPath/3.model").exists())
+    assert(new File(s"$tmpPath/3.ubj").exists())
 
     manager.cleanUpHigherVersions(2)
-    assert(!new File(s"$tmpPath/3.model").exists())
+    assert(!new File(s"$tmpPath/3.ubj").exists())
   }
 
   test("test checkpoint rounds") {
@@ -105,8 +105,8 @@ class ExternalCheckpointManagerSuite extends AnyFunSuite with TmpFolderPerSuite
       // Check only one model is kept after training
       val files = FileSystem.get(sc.hadoopConfiguration).listStatus(new Path(tmpPath))
       assert(files.length == 1)
-      assert(files.head.getPath.getName == "4.model")
-      val tmpModel = SXGBoost.loadModel(s"$tmpPath/4.model")
+      assert(files.head.getPath.getName == "4.ubj")
+      val tmpModel = SXGBoost.loadModel(s"$tmpPath/4.ubj")
       // Train next model based on prev model
       val nextModel = new XGBoostClassifier(paramMap ++ Seq("num_round" -> 8)).fit(training)
       assert(error(tmpModel) >= error(prevModel._booster))
diff --git a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/ExternalCheckpointManager.java b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/ExternalCheckpointManager.java
index 3d794756d..d5b8e8b9c 100644
--- a/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/ExternalCheckpointManager.java
+++ b/jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/ExternalCheckpointManager.java
@@ -29,7 +29,7 @@ import org.apache.hadoop.fs.Path;
 public class ExternalCheckpointManager {
 
   private Log logger = LogFactory.getLog("ExternalCheckpointManager");
-  private String modelSuffix = ".model";
+  private String modelSuffix = ".ubj";
   private Path checkpointPath;  // directory for checkpoints
   private FileSystem fs;