diff --git a/IDL/arrays.idl b/IDL/arrays.idl
index 3cff2fc..60c651f 100644
--- a/IDL/arrays.idl
+++ b/IDL/arrays.idl
@@ -537,3 +537,16 @@ struct BoundedBigArrays
 {
     short var_array_big[41925];
 };
+
+@extensibility(FINAL)
+struct LargeBasicPlainArray
+{
+    octet field1;
+    InnerBasicPlainStructHelper var_large_basic_plain_array[6291456];
+};
+
+@extensibility(FINAL)
+struct LargePlainArray
+{
+    InnerPlainStructHelper var_large_plain_array[6291456];
+};
diff --git a/IDL/helpers/basic_inner_types.idl b/IDL/helpers/basic_inner_types.idl
index 08500a5..a511c24 100644
--- a/IDL/helpers/basic_inner_types.idl
+++ b/IDL/helpers/basic_inner_types.idl
@@ -66,3 +66,17 @@ typedef InnerBitsetHelper inner_bitset_helper_alias;
 // String consts are checked here to avoid generating the related TypeObjectTest.
 const string const_string = "AAA";
 const wstring const_wstring = L"BBB";
+
+@extensibility(FINAL)
+struct InnerBasicPlainStructHelper
+{
+    long field1;
+};
+
+@extensibility(FINAL)
+struct InnerPlainStructHelper
+{
+    boolean field1;
+    long field2;
+    float field3;
+};
diff --git a/IDL/sequences.idl b/IDL/sequences.idl
index 07ee5db..9d25a0c 100644
--- a/IDL/sequences.idl
+++ b/IDL/sequences.idl
@@ -142,6 +142,12 @@ struct BoundedBigSequences
     sequence<string, 256> var_unbounded_string_large_bounded_sequence;
 };
 
+@extensibility(FINAL)
+struct LargePlainSequence
+{
+    sequence<InnerPlainStructHelper, 6291456> var_large_plain_sequence;
+};
+
 // Regression test for issue #21978.
 //{{{
 module Common_Module