diff --git a/src/ts/@overflow/commons/di/factory/instance_definition_registry.ts b/src/ts/@overflow/commons/di/factory/instance_definition_registry.ts
index e275739..9479c92 100644
--- a/src/ts/@overflow/commons/di/factory/instance_definition_registry.ts
+++ b/src/ts/@overflow/commons/di/factory/instance_definition_registry.ts
@@ -9,7 +9,7 @@ export interface InstanceDefinitionRegistry {
   removeInstanceDefinition(name: InstanceNameType): void;
   getInstanceDefinition(name: InstanceNameType): InstanceDefinition;
   containsInstanceDefinition(name: InstanceNameType): boolean;
-  getInstanceDefinitionNames(): InstanceNameType[];
+  getInstanceDefinitionNames(): Set<InstanceNameType>;
   getInstanceDefinitionCount(): number;
   isInstanceNameInUse(name: InstanceNameType): boolean;
 }