diff --git a/libwvdrmengine/mediadrm/src/WVDrmPlugin.cpp b/libwvdrmengine/mediadrm/src/WVDrmPlugin.cpp
index 164f78c2..b5893c6b 100644
--- a/libwvdrmengine/mediadrm/src/WVDrmPlugin.cpp
+++ b/libwvdrmengine/mediadrm/src/WVDrmPlugin.cpp
@@ -8,6 +8,7 @@
 
 #include "WVDrmPlugin.h"
 
+#include <endian.h>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -129,9 +130,24 @@ status_t WVDrmPlugin::getKeyRequest(
   } else {
     return android::ERROR_DRM_CANNOT_HANDLE;
   }
-
   CdmSessionId cdmSessionId(sessionId.begin(), sessionId.end());
-  CdmInitData cdmInitData(initData.begin(), initData.end());
+
+  // Build PSSH box for PSSH data in initData.
+  static const char psshPrefix[] = {
+    0, 0, 0, 0,                                     // Total size
+    'p', 's', 's', 'h',                             // "PSSH"
+    0, 0, 0, 0,                                     // Flags - must be zero
+    0xED, 0xEF, 0x8B, 0xA9, 0x79, 0xD6, 0x4A, 0xCE, // Widevine UUID
+    0xA3, 0xC8, 0x27, 0xDC, 0xD5, 0x1D, 0x21, 0xED,
+    0, 0, 0, 0                                      // Size of initData
+  };
+  CdmInitData psshBox(psshPrefix, sizeof(psshPrefix) / sizeof(uint8_t));
+  psshBox.append(reinterpret_cast<const char*>(initData.array()),
+                 initData.size());
+  uint32_t* psshBoxSize = reinterpret_cast<uint32_t*>(&psshBox[0]);
+  uint32_t* initDataSize = reinterpret_cast<uint32_t*>(&psshBox[28]);
+  *initDataSize = htonl(initData.size());
+  *psshBoxSize = htonl(psshBox.size());
 
   CdmAppParameterMap cdmParameters;
   for (size_t i = 0; i < optionalParameters.size(); ++i) {
@@ -147,7 +163,7 @@ status_t WVDrmPlugin::getKeyRequest(
   CdmKeyMessage keyRequest;
   string cdmDefaultUrl;
 
-  CdmResponseType res = mCDM->GenerateKeyRequest(cdmSessionId, cdmInitData,
+  CdmResponseType res = mCDM->GenerateKeyRequest(cdmSessionId, psshBox,
                                                  cdmLicenseType,
                                                  cdmParameters, &keyRequest,
                                                  &cdmDefaultUrl);
diff --git a/libwvdrmengine/mediadrm/test/WVDrmPlugin_test.cpp b/libwvdrmengine/mediadrm/test/WVDrmPlugin_test.cpp
index 01eeb58d..6a21ba7d 100644
--- a/libwvdrmengine/mediadrm/test/WVDrmPlugin_test.cpp
+++ b/libwvdrmengine/mediadrm/test/WVDrmPlugin_test.cpp
@@ -166,9 +166,9 @@ TEST_F(WVDrmPluginTest, GeneratesKeyRequests) {
   MockCrypto crypto;
   WVDrmPlugin plugin(&cdm, &crypto);
 
-  static const uint32_t kInitDataSize = 128;
+  static const size_t kInitDataSize = 128;
   uint8_t initDataRaw[kInitDataSize];
-  static const uint32_t kRequestSize = 256;
+  static const size_t kRequestSize = 256;
   uint8_t requestRaw[kRequestSize];
   FILE* fp = fopen("/dev/urandom", "r");
   fread(initDataRaw, sizeof(uint8_t), kInitDataSize, fp);
@@ -178,6 +178,20 @@ TEST_F(WVDrmPluginTest, GeneratesKeyRequests) {
   Vector<uint8_t> initData;
   initData.appendArray(initDataRaw, kInitDataSize);
 
+  static const uint8_t psshPrefix[] = {
+    0, 0, 0, 32 + kInitDataSize,                    // Total size
+    'p', 's', 's', 'h',                             // "PSSH"
+    0, 0, 0, 0,                                     // Flags - must be zero
+    0xED, 0xEF, 0x8B, 0xA9, 0x79, 0xD6, 0x4A, 0xCE, // Widevine UUID
+    0xA3, 0xC8, 0x27, 0xDC, 0xD5, 0x1D, 0x21, 0xED,
+    0, 0, 0, kInitDataSize                          // Size of initData
+  };
+  static const size_t kPsshPrefixSize = sizeof(psshPrefix);
+  static const size_t kPsshBoxSize = kPsshPrefixSize + kInitDataSize;
+  uint8_t psshBox[kPsshBoxSize];
+  memcpy(psshBox, psshPrefix, kPsshPrefixSize);
+  memcpy(psshBox + kPsshPrefixSize, initDataRaw, kInitDataSize);
+
   CdmKeyMessage cdmRequest(requestRaw, requestRaw + kRequestSize);
 
   KeyedVector<String8, String8> parameters;
@@ -196,8 +210,7 @@ TEST_F(WVDrmPluginTest, GeneratesKeyRequests) {
     InSequence calls;
 
     EXPECT_CALL(cdm, GenerateKeyRequest(cdmSessionId,
-                                        ElementsAreArray(initDataRaw,
-                                                         kInitDataSize),
+                                        ElementsAreArray(psshBox, kPsshBoxSize),
                                         kLicenseTypeOffline, cdmParameters, _,
                                         _))
         .WillOnce(DoAll(SetArgPointee<4>(cdmRequest),
@@ -205,10 +218,9 @@ TEST_F(WVDrmPluginTest, GeneratesKeyRequests) {
                         Return(wvcdm::KEY_MESSAGE)));
 
     EXPECT_CALL(cdm, GenerateKeyRequest(cdmSessionId,
-                                        ElementsAreArray(initDataRaw,
-                                                         kInitDataSize),
-                                        kLicenseTypeStreaming, cdmParameters,
-                                        _, _))
+                                        ElementsAreArray(psshBox, kPsshBoxSize),
+                                        kLicenseTypeStreaming, cdmParameters, _,
+                                        _))
         .WillOnce(DoAll(SetArgPointee<4>(cdmRequest),
                         SetArgPointee<5>(kDefaultUrl),
                         Return(wvcdm::KEY_MESSAGE)));