diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.1.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.1.ddl.sqlpp
new file mode 100644
index 0000000..babf75e
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.1.ddl.sqlpp
@@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+use test;
+
+create type LineItemType as closed {
+  l_orderkey: int32,
+  l_partkey: int32,
+  l_suppkey: int32,
+  l_linenumber: int32,
+  l_quantity: int32,
+  l_extendedprice: double,
+  l_discount: double,
+  l_tax: double,
+  l_returnflag: string,
+  l_linestatus: string,
+  l_shipdate: string,
+  l_commitdate: string,
+  l_receiptdate: string,
+  l_shipinstruct: string,
+  l_shipmode: string,
+  l_comment: string
+}
+
+create dataset LineItem(LineItemType) primary key l_orderkey, l_linenumber;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.2.update.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.2.update.sqlpp
new file mode 100644
index 0000000..6d593d3
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.2.update.sqlpp
@@ -0,0 +1,24 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+use test;
+
+load dataset LineItem
+using localfs
+(("path"="asterix_nc1://data/tpch0.001/lineitem.tbl"),("format"="delimited-text"),("delimiter"="|"));
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.3.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.3.query.sqlpp
new file mode 100644
index 0000000..f04f7b3
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.3.query.sqlpp
@@ -0,0 +1,24 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+use test;
+
+SELECT AVG(1) AS one FROM LineItem
+UNION ALL
+SELECT AVG(1) AS one FROM LineItem;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.1.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.1.adm
new file mode 100644
index 0000000..2e350b8
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/union/query-ASTERIXDB-1629/query-ASTERIXDB-1629.1.adm
@@ -0,0 +1,2 @@
+{ "one": 1.0 }
+{ "one": 1.0 }
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
index 7027092..3dd4ad5 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
@@ -8117,5 +8117,10 @@
         <output-dir compare="Text">query-ASTERIXDB-1354-2</output-dir>
       </compilation-unit>
     </test-case>
+    <test-case FilePath="union">
+      <compilation-unit name="query-ASTERIXDB-1629">
+        <output-dir compare="Text">query-ASTERIXDB-1629</output-dir>
+      </compilation-unit>
+    </test-case>
   </test-group>
 </test-suite>
diff --git a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/typecomputer/impl/OpenRecordConstructorResultType.java b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/typecomputer/impl/OpenRecordConstructorResultType.java
index a12bc1d..baee36a 100644
--- a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/typecomputer/impl/OpenRecordConstructorResultType.java
+++ b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/typecomputer/impl/OpenRecordConstructorResultType.java
@@ -28,6 +28,8 @@
 import org.apache.asterix.om.typecomputer.base.IResultTypeComputer;
 import org.apache.asterix.om.typecomputer.base.TypeCastUtils;
 import org.apache.asterix.om.types.ARecordType;
+import org.apache.asterix.om.types.ATypeTag;
+import org.apache.asterix.om.types.AUnionType;
 import org.apache.asterix.om.types.IAType;
 import org.apache.asterix.om.types.TypeHelper;
 import org.apache.asterix.om.util.ConstantExpressionUtil;
@@ -71,6 +73,10 @@
             String fieldName = ConstantExpressionUtil.getStringConstant(e1);
             if (fieldName != null && t2 != null && TypeHelper.isClosed(t2)) {
                 namesList.add(fieldName);
+                if (t2.getTypeTag() == ATypeTag.UNION) {
+                    AUnionType unionType = (AUnionType) t2;
+                    t2 = AUnionType.createUnknownableType(unionType.getActualType());
+                }
                 typesList.add(t2);
             } else {
                 if (canProvideAdditionFieldInfo && fieldName != null) {