diff --git a/src/serialize.cc b/src/serialize.cc
index e2ff9f42f3..f2c7cab3ce 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -2475,7 +2475,7 @@ SnapshotData::SnapshotData(const SnapshotByteSink& sink,
 
   // Set header values.
   SetHeaderValue(kCheckSumOffset, Version::Hash());
-  SetHeaderValue(kReservationsOffset, reservations.length());
+  SetHeaderValue(kNumReservationsOffset, reservations.length());
   SetHeaderValue(kPayloadLengthOffset, payload.length());
 
   // Copy reservation chunk sizes.
@@ -2496,12 +2496,12 @@ bool SnapshotData::IsSane() {
 Vector<const SerializedData::Reservation> SnapshotData::Reservations() const {
   return Vector<const Reservation>(
       reinterpret_cast<const Reservation*>(data_ + kHeaderSize),
-      GetHeaderValue(kReservationsOffset));
+      GetHeaderValue(kNumReservationsOffset));
 }
 
 
 Vector<const byte> SnapshotData::Payload() const {
-  int reservations_size = GetHeaderValue(kReservationsOffset) * kInt32Size;
+  int reservations_size = GetHeaderValue(kNumReservationsOffset) * kInt32Size;
   const byte* payload = data_ + kHeaderSize + reservations_size;
   int length = GetHeaderValue(kPayloadLengthOffset);
   DCHECK_EQ(data_ + size_, payload + length);
@@ -2556,7 +2556,9 @@ SerializedCodeData::SerializedCodeData(const List<byte>& payload,
   int reservation_size = reservations.length() * kInt32Size;
   int num_stub_keys = stub_keys->length();
   int stub_keys_size = stub_keys->length() * kInt32Size;
-  int size = kHeaderSize + reservation_size + stub_keys_size + payload.length();
+  int payload_offset = kHeaderSize + reservation_size + stub_keys_size;
+  int padded_payload_offset = POINTER_SIZE_ALIGN(payload_offset);
+  int size = padded_payload_offset + payload.length();
 
   // Allocate backing store and create result data.
   AllocateData(size);
@@ -2568,7 +2570,7 @@ SerializedCodeData::SerializedCodeData(const List<byte>& payload,
                  static_cast<uint32_t>(CpuFeatures::SupportedFeatures()));
   SetHeaderValue(kFlagHashOffset, FlagList::Hash());
   SetHeaderValue(kNumInternalizedStringsOffset, cs.num_internalized_strings());
-  SetHeaderValue(kReservationsOffset, reservations.length());
+  SetHeaderValue(kNumReservationsOffset, reservations.length());
   SetHeaderValue(kNumCodeStubKeysOffset, num_stub_keys);
   SetHeaderValue(kPayloadLengthOffset, payload.length());
 
@@ -2584,9 +2586,11 @@ SerializedCodeData::SerializedCodeData(const List<byte>& payload,
   CopyBytes(data_ + kHeaderSize + reservation_size,
             reinterpret_cast<byte*>(stub_keys->begin()), stub_keys_size);
 
+  memset(data_ + payload_offset, 0, padded_payload_offset - payload_offset);
+
   // Copy serialized data.
-  CopyBytes(data_ + kHeaderSize + reservation_size + stub_keys_size,
-            payload.begin(), static_cast<size_t>(payload.length()));
+  CopyBytes(data_ + padded_payload_offset, payload.begin(),
+            static_cast<size_t>(payload.length()));
 }
 
 
@@ -2616,15 +2620,17 @@ Vector<const SerializedData::Reservation> SerializedCodeData::Reservations()
     const {
   return Vector<const Reservation>(
       reinterpret_cast<const Reservation*>(data_ + kHeaderSize),
-      GetHeaderValue(kReservationsOffset));
+      GetHeaderValue(kNumReservationsOffset));
 }
 
 
 Vector<const byte> SerializedCodeData::Payload() const {
-  int reservations_size = GetHeaderValue(kReservationsOffset) * kInt32Size;
+  int reservations_size = GetHeaderValue(kNumReservationsOffset) * kInt32Size;
   int code_stubs_size = GetHeaderValue(kNumCodeStubKeysOffset) * kInt32Size;
-  const byte* payload =
-      data_ + kHeaderSize + reservations_size + code_stubs_size;
+  int payload_offset = kHeaderSize + reservations_size + code_stubs_size;
+  int padded_payload_offset = POINTER_SIZE_ALIGN(payload_offset);
+  const byte* payload = data_ + padded_payload_offset;
+  DCHECK(IsAligned(reinterpret_cast<intptr_t>(payload), kPointerAlignment));
   int length = GetHeaderValue(kPayloadLengthOffset);
   DCHECK_EQ(data_ + size_, payload + length);
   return Vector<const byte>(payload, length);
@@ -2636,7 +2642,7 @@ int SerializedCodeData::NumInternalizedStrings() const {
 }
 
 Vector<const uint32_t> SerializedCodeData::CodeStubKeys() const {
-  int reservations_size = GetHeaderValue(kReservationsOffset) * kInt32Size;
+  int reservations_size = GetHeaderValue(kNumReservationsOffset) * kInt32Size;
   const byte* start = data_ + kHeaderSize + reservations_size;
   return Vector<const uint32_t>(reinterpret_cast<const uint32_t*>(start),
                                 GetHeaderValue(kNumCodeStubKeysOffset));
diff --git a/src/serialize.h b/src/serialize.h
index 264bd46f46..2b7f2ade9d 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -501,12 +501,13 @@ class SerializedData {
 
  protected:
   void SetHeaderValue(int offset, uint32_t value) {
-    memcpy(reinterpret_cast<uint32_t*>(data_) + offset, &value, sizeof(value));
+    uint32_t* address = reinterpret_cast<uint32_t*>(data_ + offset);
+    memcpy(reinterpret_cast<uint32_t*>(address), &value, sizeof(value));
   }
 
   uint32_t GetHeaderValue(int offset) const {
     uint32_t value;
-    memcpy(&value, reinterpret_cast<int*>(data_) + offset, sizeof(value));
+    memcpy(&value, reinterpret_cast<int*>(data_ + offset), sizeof(value));
     return value;
   }
 
@@ -912,14 +913,16 @@ class SnapshotData : public SerializedData {
 
  private:
   bool IsSane();
-  // The data header consists of int-sized entries:
+  // The data header consists of uint32_t-sized entries:
   // [0] version hash
   // [1] number of reservation size entries
   // [2] payload length
+  // ... reservations
+  // ... serialized payload
   static const int kCheckSumOffset = 0;
-  static const int kReservationsOffset = 1;
-  static const int kPayloadLengthOffset = 2;
-  static const int kHeaderSize = (kPayloadLengthOffset + 1) * kIntSize;
+  static const int kNumReservationsOffset = kCheckSumOffset + kInt32Size;
+  static const int kPayloadLengthOffset = kNumReservationsOffset + kInt32Size;
+  static const int kHeaderSize = kPayloadLengthOffset + kInt32Size;
 };
 
 
@@ -957,7 +960,7 @@ class SerializedCodeData : public SerializedData {
 
   uint32_t SourceHash(String* source) const { return source->length(); }
 
-  // The data header consists of int-sized entries:
+  // The data header consists of uint32_t-sized entries:
   // [0] version hash
   // [1] source hash
   // [2] cpu features
@@ -966,18 +969,23 @@ class SerializedCodeData : public SerializedData {
   // [5] number of code stub keys
   // [6] number of reservation size entries
   // [7] payload length
+  // [8] payload checksum part 1
+  // [9] payload checksum part 2
+  // ... reservations
+  // ... code stub keys
+  // ... serialized payload
   static const int kVersionHashOffset = 0;
-  static const int kSourceHashOffset = 1;
-  static const int kCpuFeaturesOffset = 2;
-  static const int kFlagHashOffset = 3;
-  static const int kNumInternalizedStringsOffset = 4;
-  static const int kReservationsOffset = 5;
-  static const int kNumCodeStubKeysOffset = 6;
-  static const int kPayloadLengthOffset = 7;
-  static const int kChecksum1Offset = 8;
-  static const int kChecksum2Offset = 9;
-  static const int kHeaderSize =
-      POINTER_SIZE_ALIGN((kChecksum2Offset + 1) * kIntSize);
+  static const int kSourceHashOffset = kVersionHashOffset + kInt32Size;
+  static const int kCpuFeaturesOffset = kSourceHashOffset + kInt32Size;
+  static const int kFlagHashOffset = kCpuFeaturesOffset + kInt32Size;
+  static const int kNumInternalizedStringsOffset = kFlagHashOffset + kInt32Size;
+  static const int kNumReservationsOffset =
+      kNumInternalizedStringsOffset + kInt32Size;
+  static const int kNumCodeStubKeysOffset = kNumReservationsOffset + kInt32Size;
+  static const int kPayloadLengthOffset = kNumCodeStubKeysOffset + kInt32Size;
+  static const int kChecksum1Offset = kPayloadLengthOffset + kInt32Size;
+  static const int kChecksum2Offset = kChecksum1Offset + kInt32Size;
+  static const int kHeaderSize = kChecksum2Offset + kInt32Size;
 };
 } }  // namespace v8::internal