diff --git a/source/Ox.UI/js/Bar/Progressbar.js b/source/Ox.UI/js/Bar/Progressbar.js
index 2db32f01..74b3b905 100644
--- a/source/Ox.UI/js/Bar/Progressbar.js
+++ b/source/Ox.UI/js/Bar/Progressbar.js
@@ -43,7 +43,10 @@ Ox.Progressbar = function(options, self) {
             cancelled: toggleCancelled,
             paused: togglePaused,
             progress: function() {
-                self.options.progress = Ox.limit(self.options.progress, 0, 1);
+                self.indeterminate = self.options.progress == -1;
+                if (self.options.progress != -1) {
+                    self.options.progress = Ox.limit(self.options.progress, 0, 1);
+                }
                 !self.options.paused && !self.options.cancelled && setProgress(true);
             }
         })