diff --git a/paimon-core/src/main/java/org/apache/paimon/schema/TableSchema.java b/paimon-core/src/main/java/org/apache/paimon/schema/TableSchema.java
index 1322c4cdb35e5..18bf3c893602d 100644
--- a/paimon-core/src/main/java/org/apache/paimon/schema/TableSchema.java
+++ b/paimon-core/src/main/java/org/apache/paimon/schema/TableSchema.java
@@ -67,7 +67,7 @@ public class TableSchema implements Serializable {
 
     private final List<String> primaryKeys;
 
-    private List<String> bucketKeys;
+    private final List<String> bucketKeys;
 
     private final int numBucket;
 
@@ -121,10 +121,11 @@ public TableSchema(
         trimmedPrimaryKeys();
 
         // try to validate and initalize the bucket keys
-        bucketKeys = originalBucketKeys();
-        if (bucketKeys.isEmpty()) {
-            bucketKeys = trimmedPrimaryKeys();
+        List<String> tmpBucketKeys = originalBucketKeys();
+        if (tmpBucketKeys.isEmpty()) {
+            tmpBucketKeys = trimmedPrimaryKeys();
         }
+        bucketKeys = tmpBucketKeys;
         numBucket = CoreOptions.fromMap(options).bucket();
     }
 
diff --git a/paimon-core/src/main/java/org/apache/paimon/table/BucketSpec.java b/paimon-core/src/main/java/org/apache/paimon/table/BucketSpec.java
index 036bc331d6a5e..e6dc7a5cf7ccb 100644
--- a/paimon-core/src/main/java/org/apache/paimon/table/BucketSpec.java
+++ b/paimon-core/src/main/java/org/apache/paimon/table/BucketSpec.java
@@ -29,9 +29,9 @@
  */
 public class BucketSpec {
 
-    private BucketMode bucketMode;
-    private List<String> bucketKeys;
-    private int numBucket;
+    private final BucketMode bucketMode;
+    private final List<String> bucketKeys;
+    private final int numBucket;
 
     public BucketSpec(BucketMode bucketMode, List<String> bucketKeys, int numBucket) {
         this.bucketMode = bucketMode;