diff --git a/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java b/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java
index a96fef04df..8f3d382849 100644
--- a/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java
+++ b/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java
@@ -156,6 +156,12 @@ protected <R> Iterator<R> query(Query query,
         } catch (DriverException e) {
             LOG.debug("Failed to query [{}], detail statement: {}",
                       query, selects, e);
+            // Closing the iterator
+            try {
+                rs.close();
+            } catch (Exception e2) {
+                LOG.error("Got error {} when closing iterator for query {}", e2, query);
+            }
             throw new BackendException("Failed to query [%s]", e, query);
         }
 
diff --git a/hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlTable.java b/hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlTable.java
index 2a06beab95..3417ee21ab 100644
--- a/hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlTable.java
+++ b/hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlTable.java
@@ -477,6 +477,12 @@ protected <R> Iterator<R> query(Session session, Query query,
                 rs.extend(parser.apply(query, results));
             }
         } catch (SQLException e) {
+            // Closing the iterator
+            try {
+                rs.close();
+            } catch (Exception e2) {
+                LOG.error("Got error {} when closing iterator for query {}", e2, query);
+            }
             throw new BackendException("Failed to query [%s]", e, query);
         }