diff --git a/src/puppet-mock/puppet-mock.ts b/src/puppet-mock/puppet-mock.ts
index 4b2d22c12c98152349321a23ef93cbeab045a158..84e4ef2a8e31b1a47ca8d287c5d3680639421d32 100644
--- a/src/puppet-mock/puppet-mock.ts
+++ b/src/puppet-mock/puppet-mock.ts
@@ -245,9 +245,9 @@ export class PuppetMock extends Puppet {
     const payload: RoomPayload = {
       topic          : 'mock topic',
       memberIdList   : [],
-      nameMap        : {} as any,
-      roomAliasMap   : {} as any,
-      contactAliasMap: {} as any,
+      nameMap         : new Map<string, string>(),
+      roomAliasMap    : new Map<string, string>(),
+      contactAliasMap : new Map<string, string>(),
     }
 
     return payload