diff --git a/page-search-api/src/main/java/pt/arquivo/services/solr/SolrSearchService.java b/page-search-api/src/main/java/pt/arquivo/services/solr/SolrSearchService.java
index 0464cef..456705c 100644
--- a/page-search-api/src/main/java/pt/arquivo/services/solr/SolrSearchService.java
+++ b/page-search-api/src/main/java/pt/arquivo/services/solr/SolrSearchService.java
@@ -85,7 +85,7 @@ private SolrQuery convertSearchQuery(SearchQuery searchQuery) {
         // enable highlighting
         solrQuery.setHighlight(true);
 
-        if (searchQuery.getCollection() != null) {
+        if (searchQuery.isSearchByCollection()) {
             boolean multipleCollection = false;
             StringBuilder stringBuilder = new StringBuilder();
             stringBuilder.append("collection:");