diff --git a/src/main/java/com/alibaba/druid/wall/spi/WallVisitorUtils.java b/src/main/java/com/alibaba/druid/wall/spi/WallVisitorUtils.java
index c768f2b2ac..5d42d097bd 100644
--- a/src/main/java/com/alibaba/druid/wall/spi/WallVisitorUtils.java
+++ b/src/main/java/com/alibaba/druid/wall/spi/WallVisitorUtils.java
@@ -1506,8 +1506,7 @@ public class WallVisitorUtils {
             return;
         }
 
-        if (WallVisitorUtils.queryBlockFromIsNull(visitor, x.getLeft())
-            || WallVisitorUtils.queryBlockFromIsNull(visitor, x.getRight())) {
+        if (WallVisitorUtils.queryBlockFromIsNull(visitor, x.getRight())) {
             boolean isTopUpdateStatement = false;
             SQLObject selectParent = x.getParent();
             while (selectParent instanceof SQLUnionQuery //
diff --git a/src/test/java/com/alibaba/druid/bvt/filter/wall/MustParameterizedTest3.java b/src/test/java/com/alibaba/druid/bvt/filter/wall/MustParameterizedTest3.java
index 9dc6f82cc4..406cad11e8 100644
--- a/src/test/java/com/alibaba/druid/bvt/filter/wall/MustParameterizedTest3.java
+++ b/src/test/java/com/alibaba/druid/bvt/filter/wall/MustParameterizedTest3.java
@@ -38,7 +38,8 @@ public class MustParameterizedTest3 extends TestCase {
         Assert.assertTrue(WallUtils.isValidateMySql("select * from t where id  = ? ORDER BY 1", config));
         Assert.assertTrue(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = ?", config));
         Assert.assertFalse(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = 7", config));
-        Assert.assertFalse(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = ? union select * from t", config));
+        Assert.assertTrue(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = ? union select * from t", config));
+        Assert.assertFalse(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = ? union select 1, 2, 3", config));
         Assert.assertFalse(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = ? union select * from t fid = fid", config));
         Assert.assertFalse(WallUtils.isValidateMySql("select 1, 2, 3 from t where id  = ? union select * from t fid > 5", config));
     }
diff --git a/src/test/java/com/alibaba/druid/bvt/filter/wall/OracleWallTest6.java b/src/test/java/com/alibaba/druid/bvt/filter/wall/OracleWallTest6.java
new file mode 100644
index 0000000000..521b51eb2c
--- /dev/null
+++ b/src/test/java/com/alibaba/druid/bvt/filter/wall/OracleWallTest6.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright 1999-2011 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.druid.bvt.filter.wall;
+
+import junit.framework.TestCase;
+
+import org.junit.Assert;
+
+import com.alibaba.druid.wall.WallUtils;
+
+public class OracleWallTest6 extends TestCase {
+
+    public void test_true() throws Exception {
+        String sql = //
+        "select *"
+        + "  from (SELECT Distinct notice.NSERIAL,"
+        + "                        unit.CUNIT_name,"
+        + "                        us.CUSER_name,"
+        + "                        to_char(notice.DCREATE, 'yyyy-mm-dd') DCREATE,"
+        + "                        notice.csubject,"
+        + "                        notice.ccontent"
+        + "          From mewp_notice_info notice, bas_user us, bas_unit unit"
+        + "          Left Join bas_area xsArea"
+        + "            On unit.ccounty_code = xsArea.Carea_Code"
+        + "          Left Join bas_area pqArea"
+        + "            On unit.cpiece_code = pqArea.Carea_Code"
+        + "          Left Join bas_area xzArea"
+        + "            On unit.cctown_code = xzArea.Carea_Code"
+        + "          Left Join bas_area czArea"
+        + "            On unit.cvillage_code = czArea.Carea_Code"
+        + "         Where notice.cunit_code = unit.cunit_code"
+        + "           And notice.cuser_id = us.cuser_code"
+        + "           And notice.nstate = 4"
+        + "           And (notice.nrole = '****' or notice.nrole = '202')"
+        + "           and notice.cunit_code in"
+        + "               (select 'CP0008'"
+        + "                  from dual"
+        + "                union"
+        + "                select Distinct t.cunit_code"
+        + "                  from bas_unit t, bas_area us"
+        + "                 where t.ccounty_code = us.carea_code"
+        + "                   and t.ccounty_code = 'CP'"
+        + "                   and t.ctype = '201'"
+        + "                union"
+        + "                select Distinct auser.cunit_code"
+        + "                  from bas_user auser, bas_user_role ur"
+        + "                 where auser.cuser_code = ur.cuser_code"
+        + "                   and (ur.nrole_id = '1' or ur.nrole_id = '20'))"
+        + "         order by DCREATE desc)"
+        + " where rownum <= 30";
+        Assert.assertTrue(WallUtils.isValidateOracle(sql));
+    }
+}