diff --git a/app/indexers/work_indexer.rb b/app/indexers/work_indexer.rb
index 9442b999..de68565f 100644
--- a/app/indexers/work_indexer.rb
+++ b/app/indexers/work_indexer.rb
@@ -59,7 +59,7 @@ def related_record_title_markup(ursus_url, title)
   def add_dates(solr_doc)
     valid_dates = solr_dates
     solr_doc['date_dtsim'] = valid_dates if valid_dates
-    solr_doc['date_dtsort'] = solr_doc['date_dtsim'][0] if solr_doc['date_dtsort']
+    solr_doc['date_dtsort'] = solr_doc['date_dtsim'][0] if solr_doc['date_dtsim']
   end
 
   def combined_subject
diff --git a/spec/indexers/work_indexer_spec.rb b/spec/indexers/work_indexer_spec.rb
index eabab369..4f722279 100644
--- a/spec/indexers/work_indexer_spec.rb
+++ b/spec/indexers/work_indexer_spec.rb
@@ -303,6 +303,7 @@
       it 'indexes the year' do
         expect(solr_document['year_isim']).to eq [1940]
         expect(solr_document['date_dtsim']).to eq [Date.strptime('1940', "%Y").to_time.utc.iso8601]
+        expect(solr_document['date_dtsort']).to eq '1940-01-01T00:00:00Z'
       end
     end
 
@@ -345,6 +346,7 @@
       it 'indexes the earliest year' do
         expect(solr_document['sort_year_isi']).to eq 1940
         expect(solr_document['date_dtsim']).to eq [Date.strptime('1940-10-15', "%Y-%m-%d").to_time.utc.iso8601]
+        expect(solr_document['date_dtsort']).to eq '1940-10-15T00:00:00Z'
       end
     end
 
@@ -372,6 +374,7 @@
       it 'indexes the earliest year' do
         expect(solr_document['sort_year_isi']).to eq 1934
         expect(solr_document['date_dtsim']).to eq [Date.strptime('1934-06', "%Y-%m").to_time.utc.iso8601, Date.strptime('1937-07', "%Y-%m").to_time.utc.iso8601]
+        expect(solr_document['date_dtsort']).to eq '1934-06-01T00:00:00Z'
       end
     end