diff --git a/static/scripts/viz/trackster_ui.js b/static/scripts/viz/trackster_ui.js
index 83d565652c7..322dc123fcf 100644
--- a/static/scripts/viz/trackster_ui.js
+++ b/static/scripts/viz/trackster_ui.js
@@ -191,8 +191,7 @@ var TracksterUI = base.Base.extend({
         $.when( view.load_chroms_deferred ).then(function(chrom_info) {
             // Viewport config.
             if (viewport_config) {
-                var 
-                    chrom = viewport_config.chrom,
+                var chrom = viewport_config.chrom,
                     start = viewport_config.start,
                     end = viewport_config.end,
                     overview_drawable_name = viewport_config.overview;
@@ -200,6 +199,10 @@ var TracksterUI = base.Base.extend({
                 if (chrom && (start !== undefined) && end) {
                     view.change_chrom(chrom, start, end);
                 }
+                else {
+                    // No valid viewport, so use first chromosome.
+                    view.change_chrom(chrom_info[0].chrom);
+                }
             }
             else {
                 // No viewport, so use first chromosome.