diff --git a/leveldb-api/src/main/java/org/iq80/leveldb/WriteBatch.java b/leveldb-api/src/main/java/org/iq80/leveldb/WriteBatch.java
index eb462ced..8c984c57 100644
--- a/leveldb-api/src/main/java/org/iq80/leveldb/WriteBatch.java
+++ b/leveldb-api/src/main/java/org/iq80/leveldb/WriteBatch.java
@@ -59,6 +59,7 @@ public interface WriteBatch
      * The size of the database changes caused by this batch.
      * Note: This number is tied to implementation details, and may change across
      * releases. It is intended for LevelDB usage metrics.
+     * WriteBatch header has an 8-byte sequence number followed by a 4-byte count.
      * @return size
      */
     long approximateSize();
diff --git a/leveldb/src/test/java/org/iq80/leveldb/impl/DbImplTest.java b/leveldb/src/test/java/org/iq80/leveldb/impl/DbImplTest.java
index 72df8258..ac9b0209 100644
--- a/leveldb/src/test/java/org/iq80/leveldb/impl/DbImplTest.java
+++ b/leveldb/src/test/java/org/iq80/leveldb/impl/DbImplTest.java
@@ -126,8 +126,20 @@ public void testEmptyBatch()
 
         // write an empty batch
         WriteBatch batch = db.createWriteBatch();
-        batch.close();
+        batch.put("foobar".getBytes(UTF_8), "tgz".getBytes(UTF_8));
+        batch.put("bob".getBytes(UTF_8), "tar".getBytes(UTF_8));
+        WriteBatch source = db.createWriteBatch();
+        source.put("foobar".getBytes(UTF_8), "tgz".getBytes(UTF_8));
+        source.put("bob".getBytes(UTF_8), "tar".getBytes(UTF_8));
+        batch.clear();
+        assertEquals(12, batch.approximateSize());
+        batch.append(source);
+        batch.append(source);
+        assertEquals(source.approximateSize() * 2  -12, batch.approximateSize());
+        batch.clear();
+        assertEquals(12, batch.approximateSize());
         db.write(batch);
+        batch.close();
 
         // close the db
         db.close();