diff --git a/odoo/addons/base/models/ir_qweb_fields.py b/odoo/addons/base/models/ir_qweb_fields.py
index 6ee26f0c085..d08c8c14cd8 100644
--- a/odoo/addons/base/models/ir_qweb_fields.py
+++ b/odoo/addons/base/models/ir_qweb_fields.py
@@ -577,6 +577,10 @@ class DurationConverter(models.AbstractModel):
         r = round((value * factor) / round_to) * round_to
 
         sections = []
+        sign = ''
+        if value < 0:
+            r = -r
+            sign = '-'
 
         if options.get('digital'):
             for unit, label, secs_per_unit in TIMEDELTA_UNITS:
@@ -585,14 +589,9 @@ class DurationConverter(models.AbstractModel):
                 v, r = divmod(r, secs_per_unit)
                 if not v and (secs_per_unit > factor or secs_per_unit < round_to):
                     continue
-                if len(sections):
-                    sections.append(':')
-                sections.append("%02.0f" % int(round(v)))
-            return ''.join(sections)
+                sections.append(u"%02.0f" % int(round(v)))
+            return sign + u':'.join(sections)
 
-        if value < 0:
-            r = -r
-            sections.append('-')
         for unit, label, secs_per_unit in TIMEDELTA_UNITS:
             v, r = divmod(r, secs_per_unit)
             if not v:
@@ -607,7 +606,9 @@ class DurationConverter(models.AbstractModel):
             if section:
                 sections.append(section)
 
-        return ' '.join(sections)
+        if sign:
+            sections.insert(0, sign)
+        return u' '.join(sections)
 
 
 class RelativeDatetimeConverter(models.AbstractModel):
diff --git a/odoo/addons/test_converter/tests/test_html.py b/odoo/addons/test_converter/tests/test_html.py
index 9a56838585e..49544b84fba 100644
--- a/odoo/addons/test_converter/tests/test_html.py
+++ b/odoo/addons/test_converter/tests/test_html.py
@@ -333,6 +333,11 @@ class TestDurationExport(TestBasicExport):
         result = converter(72, {'unit': 'second'}, {'lang': 'fr_FR'})
         self.assertEqual(result, u"1 minute 12 secondes")
 
+    def test_negative_digital(self):
+        converter = self.get_converter('float', 'duration')
+        result = converter(-90, {'unit': 'minute', 'round': 'minute', 'digital': True}, {'lang': 'fr_FR'})
+        self.assertEqual(result, u'-01:30')
+
 
 class TestRelativeDatetime(TestBasicExport):
     # not sure how a test based on "current time" should be tested. Even less