diff --git a/build-data/BuildArtwork.groovy b/build-data/BuildArtwork.groovy
index b28a1e5a..a9c66dd6 100755
--- a/build-data/BuildArtwork.groovy
+++ b/build-data/BuildArtwork.groovy
@@ -87,5 +87,5 @@ void build(ids, section, db, query) {
 
 
 
-build(MediaDetection.seriesIndex.object.id as Set, 'thetvdb', TheTVDB, 'poster')
-build(MediaDetection.movieIndex.object.tmdbId as Set, 'themoviedb', TheMovieDB, 'posters')
+build(MediaDetection.seriesIndex.object.id as HashSet, 'thetvdb', TheTVDB, 'poster')
+build(MediaDetection.movieIndex.object.tmdbId as HashSet, 'themoviedb', TheMovieDB, 'posters')