diff --git a/addons/web/static/src/js/formats.js b/addons/web/static/src/js/formats.js
index eb7d6c335ac..d35a28f36b7 100644
--- a/addons/web/static/src/js/formats.js
+++ b/addons/web/static/src/js/formats.js
@@ -101,7 +101,12 @@ openerp.web.format_value = function (value, descriptor, value_if_empty) {
             formatted[0] = openerp.web.insert_thousand_seps(formatted[0]);
             return formatted.join(l10n.decimal_point);
         case 'float_time':
-            return _.str.sprintf("%02d:%02d",
+            var pattern = '%02d:%02d';
+            if (value < 0) {
+                value = Math.abs(value);
+                pattern = '-' + pattern;
+            }
+            return _.str.sprintf(pattern,
                     Math.floor(value),
                     Math.round((value % 1) * 60));
         case 'many2one':
diff --git a/addons/web/static/test/formats.js b/addons/web/static/test/formats.js
index 640eaaadca7..2e292af41c8 100644
--- a/addons/web/static/test/formats.js
+++ b/addons/web/static/test/formats.js
@@ -71,6 +71,15 @@ $(document).ready(function () {
         strictEqual(
             openerp.web.format_value(0.0085, {type:'float', widget:'float_time'}),
             '00:01');
+        strictEqual(
+            openerp.web.format_value(-1.0, {type:'float', widget:'float_time'}),
+            '-01:00');
+        strictEqual(
+            openerp.web.format_value(-0.9853, {type:'float', widget:'float_time'}),
+            '-00:59');
+        strictEqual(
+            openerp.web.format_value(-0.0085, {type:'float', widget:'float_time'}),
+            '-00:01');
     });
     test("format_float", function () {
         var fl = 12.1234;