diff --git a/core/src/main/java/org/opensearch/sql/planner/physical/FlattenOperator.java b/core/src/main/java/org/opensearch/sql/planner/physical/FlattenOperator.java
index e42d8b65bd..16a4c1dd87 100644
--- a/core/src/main/java/org/opensearch/sql/planner/physical/FlattenOperator.java
+++ b/core/src/main/java/org/opensearch/sql/planner/physical/FlattenOperator.java
@@ -88,10 +88,11 @@ private static ExprValue flattenExprValueAtPath(ExprValue rootExprValue, String
     }
 
     ExprValue childExprValue = exprValueMap.get(path);
-    if (!childExprValue.isNull() && !childExprValue.isMissing()) {
-      exprValueMap.putAll(ExprValueUtils.getTupleValue(childExprValue));
+    if (childExprValue.isNull() || childExprValue.isMissing()) {
+      return rootExprValue;
     }
 
+    exprValueMap.putAll(ExprValueUtils.getTupleValue(childExprValue));
     return ExprTupleValue.fromExprValueMap(exprValueMap);
   }
 }
diff --git a/core/src/test/java/org/opensearch/sql/planner/logical/LogicalFlattenTest.java b/core/src/test/java/org/opensearch/sql/planner/logical/LogicalFlattenTest.java
index f291165559..75a800af00 100644
--- a/core/src/test/java/org/opensearch/sql/planner/logical/LogicalFlattenTest.java
+++ b/core/src/test/java/org/opensearch/sql/planner/logical/LogicalFlattenTest.java
@@ -113,14 +113,17 @@ void testInvalidName() {
 
   @Test
   void testInvalidDuplicate() {
-    Exception ex;
+    String msg;
 
-    ex = assertThrows(SemanticCheckException.class, () -> executeFlatten("duplicate"));
-    assertEquals("Flatten command cannot overwrite fields: integer_value", ex.getMessage());
+    msg =
+        assertThrows(SemanticCheckException.class, () -> executeFlatten("duplicate")).getMessage();
+    assertTrue(msg.contains("integer_value"));
 
-    ex = assertThrows(SemanticCheckException.class, () -> executeFlatten("duplicate_2"));
-    assertEquals(
-        "Flatten command cannot overwrite fields: integer_value, double_value", ex.getMessage());
+    msg =
+        assertThrows(SemanticCheckException.class, () -> executeFlatten("duplicate_2"))
+            .getMessage();
+    assertTrue(msg.contains("integer_value"));
+    assertTrue(msg.contains("double_value"));
   }
 
   /**