diff --git a/cpp/src/arrow/compute/row/compare_test.cc b/cpp/src/arrow/compute/row/compare_test.cc
index 2b8f4d97561..9bc839cf424 100644
--- a/cpp/src/arrow/compute/row/compare_test.cc
+++ b/cpp/src/arrow/compute/row/compare_test.cc
@@ -386,8 +386,8 @@ TEST(KeyCompare, LARGE_MEMORY_TEST(CompareColumnsToRowsOver4GBFixedLength)) {
       RowTableImpl row_table_right,
       RepeatRowTableUntil(MakeRowTableFromExecBatch(batch_left).ValueUnsafe(),
                           num_rows_row_table));
-  // The row table must not contain a third buffer.
-  ASSERT_EQ(row_table_right.var_length_rows(), NULLPTR);
+  // The row table must be fixed length.
+  ASSERT_TRUE(row_table_right.metadata().is_fixed_length);
   // The row data must be greater than 4GB.
   ASSERT_GT(row_table_right.buffer_size(1), k4GB);