diff --git a/packager/mpd/base/mpd_utils.cc b/packager/mpd/base/mpd_utils.cc
index f00d85cc83..9c173413c1 100644
--- a/packager/mpd/base/mpd_utils.cc
+++ b/packager/mpd/base/mpd_utils.cc
@@ -319,7 +319,8 @@ Element GenerateMarlinContentIds(const std::string& key_id) {
   Element marlin_content_id;
   marlin_content_id.name = kMarlinContentIdName;
   marlin_content_id.content =
-      kMarlinContentIdPrefix + base::HexEncode(key_id.data(), key_id.size());
+      kMarlinContentIdPrefix +
+      base::ToLowerASCII(base::HexEncode(key_id.data(), key_id.size()));
 
   Element marlin_content_ids;
   marlin_content_ids.name = kMarlinContentIdsName;
diff --git a/packager/mpd/base/mpd_utils_unittest.cc b/packager/mpd/base/mpd_utils_unittest.cc
new file mode 100644
index 0000000000..b82b8f0a69
--- /dev/null
+++ b/packager/mpd/base/mpd_utils_unittest.cc
@@ -0,0 +1,119 @@
+// Copyright 2018 Google LLC. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/mpd/base/mpd_utils.h"
+
+#include <gtest/gtest.h>
+#include <memory>
+
+#include "packager/mpd/base/adaptation_set.h"
+#include "packager/mpd/base/mpd_options.h"
+#include "packager/mpd/test/mpd_builder_test_helper.h"
+#include "packager/mpd/test/xml_compare.h"
+
+namespace shaka {
+namespace {
+const char kNoLanguage[] = "";
+}  // namespace
+
+class TestableAdaptationSet : public AdaptationSet {
+ public:
+  TestableAdaptationSet(const MpdOptions& mpd_options,
+                        uint32_t* representation_counter)
+      : AdaptationSet(kNoLanguage, mpd_options, representation_counter) {}
+};
+
+class MpdUtilsTest : public ::testing::Test {
+ public:
+  MpdUtilsTest() : adaptation_set_(mpd_options_, &representation_counter_) {}
+
+ protected:
+  MpdOptions mpd_options_;
+  uint32_t representation_counter_ = 0;
+  TestableAdaptationSet adaptation_set_;
+};
+
+TEST_F(MpdUtilsTest, ContentProtectionGeneral) {
+  const char kMediaInfoWithContentProtection[] =
+      "video_info {"
+      "  codec: 'avc1'"
+      "  width: 1920"
+      "  height: 1080"
+      "  time_scale: 3000"
+      "  frame_duration: 100"
+      "}"
+      "protected_content {"
+      "  default_key_id: '0123456789\x3A\x3B\x3C\x3D\x3E\x3F'"
+      "  content_protection_entry {"
+      "    uuid: 'my_uuid'"
+      "    pssh: 'my_pssh'"
+      "  }"
+      "}"
+      "container_type: 1";
+  const MediaInfo media_info =
+      ConvertToMediaInfo(kMediaInfoWithContentProtection);
+
+  AddContentProtectionElements(media_info, &adaptation_set_);
+  ASSERT_TRUE(adaptation_set_.AddRepresentation(media_info));
+
+  const char kExpectedOutput[] =
+      "<AdaptationSet contentType='video' width='1920'"
+      "    height='1080' frameRate='3000/100'>"
+      "  <ContentProtection value='cenc'"
+      "      schemeIdUri='urn:mpeg:dash:mp4protection:2011'"
+      "      cenc:default_KID='30313233-3435-3637-3839-3a3b3c3d3e3f'/>"
+      "  <ContentProtection schemeIdUri='urn:uuid:my_uuid'>"
+      "    <cenc:pssh>bXlfcHNzaA==</cenc:pssh>"
+      "  </ContentProtection>"
+      "  <Representation id='0' bandwidth='0' codecs='avc1'"
+      "   mimeType='video/mp4'/>"
+      "</AdaptationSet>";
+  EXPECT_THAT(adaptation_set_.GetXml().get(), XmlNodeEqual(kExpectedOutput));
+}
+
+TEST_F(MpdUtilsTest, ContentProtectionMarlin) {
+  const char kMediaInfoWithContentProtection[] =
+      "video_info {"
+      "  codec: 'avc1'"
+      "  width: 1920"
+      "  height: 1080"
+      "  time_scale: 3000"
+      "  frame_duration: 100"
+      "}"
+      "protected_content {"
+      "  default_key_id: '0123456789\x3A\x3B\x3C\x3D\x3E\x3F'"
+      "  content_protection_entry {"
+      "    uuid: '5e629af5-38da-4063-8977-97ffbd9902d4'"
+      "  }"
+      "}"
+      "container_type: 1";
+  const MediaInfo media_info =
+      ConvertToMediaInfo(kMediaInfoWithContentProtection);
+
+  AddContentProtectionElements(media_info, &adaptation_set_);
+  ASSERT_TRUE(adaptation_set_.AddRepresentation(media_info));
+
+  const char kExpectedOutput[] =
+      "<AdaptationSet contentType='video' width='1920'"
+      "    height='1080' frameRate='3000/100'>"
+      "  <ContentProtection value='cenc'"
+      "      schemeIdUri='urn:mpeg:dash:mp4protection:2011'"
+      "      cenc:default_KID='30313233-3435-3637-3839-3a3b3c3d3e3f'/>"
+      "  <ContentProtection"
+      "      schemeIdUri='urn:uuid:5e629af5-38da-4063-8977-97ffbd9902d4'>"
+      "    <mas:MarlinContentIds>"
+      "      <mas:MarlinContentId>"
+      "        urn:marlin:kid:303132333435363738393a3b3c3d3e3f"
+      "      </mas:MarlinContentId>"
+      "    </mas:MarlinContentIds>"
+      "  </ContentProtection>"
+      "  <Representation id='0' bandwidth='0' codecs='avc1'"
+      "   mimeType='video/mp4'/>"
+      "</AdaptationSet>";
+  EXPECT_THAT(adaptation_set_.GetXml().get(), XmlNodeEqual(kExpectedOutput));
+}
+
+}  // namespace shaka
diff --git a/packager/mpd/mpd.gyp b/packager/mpd/mpd.gyp
index d3d95834b3..4951563c53 100644
--- a/packager/mpd/mpd.gyp
+++ b/packager/mpd/mpd.gyp
@@ -100,6 +100,7 @@
         'base/adaptation_set_unittest.cc',
         'base/bandwidth_estimator_unittest.cc',
         'base/mpd_builder_unittest.cc',
+        'base/mpd_utils_unittest.cc',
         'base/period_unittest.cc',
         'base/representation_unittest.cc',
         'base/simple_mpd_notifier_unittest.cc',