diff --git a/src/snapshot/code-serializer.cc b/src/snapshot/code-serializer.cc
index 601659a149..8d2f5d9339 100644
--- a/src/snapshot/code-serializer.cc
+++ b/src/snapshot/code-serializer.cc
@@ -315,10 +315,6 @@ SerializedCodeData::SerializedCodeData(const List<byte>* payload,
   SetHeaderValue(kNumCodeStubKeysOffset, num_stub_keys);
   SetHeaderValue(kPayloadLengthOffset, payload->length());
 
-  Checksum checksum(payload->ToConstVector());
-  SetHeaderValue(kChecksum1Offset, checksum.a());
-  SetHeaderValue(kChecksum2Offset, checksum.b());
-
   // Copy reservation chunk sizes.
   CopyBytes(data_ + kHeaderSize, reinterpret_cast<byte*>(reservations.begin()),
             reservation_size);
@@ -332,6 +328,10 @@ SerializedCodeData::SerializedCodeData(const List<byte>* payload,
   // Copy serialized data.
   CopyBytes(data_ + padded_payload_offset, payload->begin(),
             static_cast<size_t>(payload->length()));
+
+  Checksum checksum(DataWithoutHeader());
+  SetHeaderValue(kChecksum1Offset, checksum.a());
+  SetHeaderValue(kChecksum2Offset, checksum.b());
 }
 
 SerializedCodeData::SanityCheckResult SerializedCodeData::SanityCheck(
@@ -350,7 +350,7 @@ SerializedCodeData::SanityCheckResult SerializedCodeData::SanityCheck(
     return CPU_FEATURES_MISMATCH;
   }
   if (flags_hash != FlagList::Hash()) return FLAGS_MISMATCH;
-  if (!Checksum(Payload()).Check(c1, c2)) return CHECKSUM_MISMATCH;
+  if (!Checksum(DataWithoutHeader()).Check(c1, c2)) return CHECKSUM_MISMATCH;
   return CHECK_SUCCESS;
 }
 
diff --git a/src/snapshot/code-serializer.h b/src/snapshot/code-serializer.h
index 6a5937d728..e82a7d5dd6 100644
--- a/src/snapshot/code-serializer.h
+++ b/src/snapshot/code-serializer.h
@@ -115,6 +115,10 @@ class SerializedCodeData : public SerializedData {
   SerializedCodeData(const byte* data, int size)
       : SerializedData(const_cast<byte*>(data), size) {}
 
+  Vector<const byte> DataWithoutHeader() const {
+    return Vector<const byte>(data_ + kHeaderSize, size_ - kHeaderSize);
+  }
+
   SanityCheckResult SanityCheck(Isolate* isolate,
                                 uint32_t expected_source_hash) const;
   // The data header consists of uint32_t-sized entries:
diff --git a/src/snapshot/deserializer.cc b/src/snapshot/deserializer.cc
index d8df2d0d56..269a9a890d 100644
--- a/src/snapshot/deserializer.cc
+++ b/src/snapshot/deserializer.cc
@@ -163,12 +163,14 @@ MaybeHandle<HeapObject> Deserializer::DeserializeObject(Isolate* isolate) {
 Deserializer::~Deserializer() {
   // TODO(svenpanne) Re-enable this assertion when v8 initialization is fixed.
   // DCHECK(source_.AtEOF());
+#ifdef DEBUG
   for (int space = 0; space < kNumberOfPreallocatedSpaces; space++) {
     int chunk_index = current_chunk_[space];
     CHECK_EQ(reservations_[space].length(), chunk_index + 1);
     CHECK_EQ(reservations_[space][chunk_index].end, high_water_[space]);
   }
   CHECK_EQ(allocated_maps_.length(), next_map_index_);
+#endif  // DEBUG
 }
 
 // This is called on the roots.  It is the driver of the deserialization