diff --git a/packager/app/mpd_flags.cc b/packager/app/mpd_flags.cc
index bfa3864518..63bb9232e7 100644
--- a/packager/app/mpd_flags.cc
+++ b/packager/app/mpd_flags.cc
@@ -43,6 +43,11 @@ DEFINE_double(suggested_presentation_delay,
               0.0,
               "Specifies a delay, in seconds, to be added to the media "
               "presentation time. This value is used for live profile only.");
+DEFINE_string(default_language,
+              "",
+              "Any tracks tagged with this language will have "
+              "<Role ... value=\"main\" /> in the manifest.  This allows the "
+              "player to choose the correct default language for the content.");
 DEFINE_bool(generate_dash_if_iop_compliant_mpd,
             false,
             "Try to generate DASH-IF IOPv3 compliant MPD. This is best effort "
diff --git a/packager/app/mpd_flags.h b/packager/app/mpd_flags.h
index ff76e9b838..ba7f657e3a 100644
--- a/packager/app/mpd_flags.h
+++ b/packager/app/mpd_flags.h
@@ -19,6 +19,7 @@ DECLARE_double(minimum_update_period);
 DECLARE_double(min_buffer_time);
 DECLARE_double(time_shift_buffer_depth);
 DECLARE_double(suggested_presentation_delay);
+DECLARE_string(default_language);
 DECLARE_bool(generate_dash_if_iop_compliant_mpd);
 
 #endif  // APP_MPD_FLAGS_H_
diff --git a/packager/app/packager_util.cc b/packager/app/packager_util.cc
index ca7cf13003..f55224f8cf 100644
--- a/packager/app/packager_util.cc
+++ b/packager/app/packager_util.cc
@@ -177,6 +177,7 @@ bool GetMpdOptions(MpdOptions* mpd_options) {
   mpd_options->time_shift_buffer_depth = FLAGS_time_shift_buffer_depth;
   mpd_options->suggested_presentation_delay =
       FLAGS_suggested_presentation_delay;
+  mpd_options->default_language = FLAGS_default_language;
   return true;
 }
 
diff --git a/packager/mpd/base/mpd_builder.cc b/packager/mpd/base/mpd_builder.cc
index c92a772f1a..5bb3482e1f 100644
--- a/packager/mpd/base/mpd_builder.cc
+++ b/packager/mpd/base/mpd_builder.cc
@@ -413,8 +413,12 @@ AdaptationSet* MpdBuilder::AddAdaptationSet(const std::string& lang) {
   std::unique_ptr<AdaptationSet> adaptation_set(
       new AdaptationSet(adaptation_set_counter_.GetNext(), lang, mpd_options_,
                         type_, &representation_counter_));
-
   DCHECK(adaptation_set);
+
+  if (!lang.empty() && lang == mpd_options_.default_language) {
+    adaptation_set->AddRole(AdaptationSet::kRoleMain);
+  }
+
   adaptation_sets_.push_back(std::move(adaptation_set));
   return adaptation_sets_.back().get();
 }
diff --git a/packager/mpd/base/mpd_options.h b/packager/mpd/base/mpd_options.h
index 28cfac91a4..03bf117961 100644
--- a/packager/mpd/base/mpd_options.h
+++ b/packager/mpd/base/mpd_options.h
@@ -28,6 +28,7 @@ struct MpdOptions {
   double min_buffer_time;
   double time_shift_buffer_depth;
   double suggested_presentation_delay;
+  std::string default_language;
 };
 
 }  // namespace shaka