diff --git a/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/FixedLengthRowBasedKeyValueBatch.java b/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/FixedLengthRowBasedKeyValueBatch.java
index df52f9c2d5..25400beeb0 100644
--- a/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/FixedLengthRowBasedKeyValueBatch.java
+++ b/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/FixedLengthRowBasedKeyValueBatch.java
@@ -46,6 +46,8 @@ public final class FixedLengthRowBasedKeyValueBatch extends RowBasedKeyValueBatc
   public UnsafeRow appendRow(Object kbase, long koff, int klen,
                              Object vbase, long voff, int vlen) {
     // if run out of max supported rows or page size, return null
+    assert(vlen == this.vlen);
+    assert(klen == this.klen);
     if (numRows >= capacity || page == null || page.size() - pageCursor < recordLength) {
       return null;
     }