diff --git a/static/js/viewer.js b/static/js/viewer.js
index 616aacf..d621087 100644
--- a/static/js/viewer.js
+++ b/static/js/viewer.js
@@ -215,7 +215,11 @@ oml.ui.viewer = function() {
             })
             return
         }
-        annotations = Ox.sortBy(annotations, sortKey)
+        var map = {}
+        map[sortKey] = function(value) {
+            return value.toString();
+        }
+        annotations = Ox.sortBy(annotations, sortKey, map)
         oml.$ui.annotationFolder.empty();
         var visibleAnnotations = [];
         var hasAnnotations = false;