<<<
--- /django__django/django/db/models/fields/__init__.py
+++ /django__django/django/db/models/fields/__init__.py
@@ -1582,7 +1582,7 @@

     empty_strings_allowed = False
     default_error_messages = {
-        'invalid': _("'%(value)s' value has an invalid format. It must be in "
-                     "[DD] [HH:[MM:]]ss[.uuuuuu] format."),
+        'invalid': _("'%(value)s' value has an invalid format. It must be in "
+                     "[DD] [[HH:]MM:]ss[.uuuuuu] format."),
     }
     description = _("Duration")
>>>