diff --git a/src/awst_build/models/contract-class-model.ts b/src/awst_build/models/contract-class-model.ts
index 533af049..b2efdc28 100644
--- a/src/awst_build/models/contract-class-model.ts
+++ b/src/awst_build/models/contract-class-model.ts
@@ -15,6 +15,7 @@ import type { ContractClassPType } from '../ptypes'
 import { ClusteredContractClassType } from '../ptypes'
 import type { ContractOptionsDecoratorData } from './decorator-data'
 import { LogicSigClassModel } from './logic-sig-class-model'
+import '../../polyfill/set.prototype.union'
 
 export class ContractClassModel {
   public readonly isAbstract: boolean
diff --git a/src/polyfill/set.prototype.union.ts b/src/polyfill/set.prototype.union.ts
new file mode 100644
index 00000000..35a245f2
--- /dev/null
+++ b/src/polyfill/set.prototype.union.ts
@@ -0,0 +1,5 @@
+if (!Set.prototype.union) {
+  Set.prototype.union = function union<T>(this: Set<T>, other: ReadonlySet<T>) {
+    return new Set([...this, ...other])
+  }
+}