diff --git a/packages/graphql/lib/schema-builder/metadata/union.metadata.ts b/packages/graphql/lib/schema-builder/metadata/union.metadata.ts
index 52faabf70..683b5ccc4 100644
--- a/packages/graphql/lib/schema-builder/metadata/union.metadata.ts
+++ b/packages/graphql/lib/schema-builder/metadata/union.metadata.ts
@@ -1,7 +1,7 @@
 import { Type } from '@nestjs/common';
 import { ResolveTypeFn } from '../../interfaces';
 
-export interface UnionMetadata<T extends Type<unknown>[] = Type<unknown>[]> {
+export interface UnionMetadata<T extends readonly Type<unknown>[] = readonly Type<unknown>[]> {
   name: string;
   typesFn: () => T;
   id?: symbol;
diff --git a/packages/graphql/lib/type-factories/create-union-type.factory.ts b/packages/graphql/lib/type-factories/create-union-type.factory.ts
index db94f15bb..395a52d99 100644
--- a/packages/graphql/lib/type-factories/create-union-type.factory.ts
+++ b/packages/graphql/lib/type-factories/create-union-type.factory.ts
@@ -13,7 +13,7 @@ import { TypeMetadataStorage } from '../schema-builder/storages/type-metadata.st
 /**
  * Interface defining options that can be passed to `createUnionType` function.
  */
-export interface UnionOptions<T extends Type<unknown>[] = any[]> {
+export interface UnionOptions<T extends readonly Type<unknown>[] = Type<unknown>[]> {
   /**
    * Name of the union.
    */
@@ -34,13 +34,13 @@ export interface UnionOptions<T extends Type<unknown>[] = any[]> {
 
 export type ArrayElement<ArrayType extends readonly unknown[]> =
   ArrayType[number];
-export type Union<T extends any[]> = InstanceType<ArrayElement<T>>;
+export type Union<T extends readonly any[]> = InstanceType<ArrayElement<T>>;
 
 /**
  * Creates a GraphQL union type composed of types references.
  * @param options
  */
-export function createUnionType<T extends Type<unknown>[] = any[]>(
+export function createUnionType<T extends readonly Type<unknown>[] = Type<unknown>[]>(
   options: UnionOptions<T>,
 ): Union<T> {
   const { name, description, types, resolveType } = options;