diff --git a/src/parser.cc b/src/parser.cc
index b25a7b1af2..544c8c7d8d 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -859,7 +859,7 @@ FunctionLiteral* Parser::DoParseProgram(CompilationInfo* info,
   FunctionLiteral* result = NULL;
   { Scope* scope = NewScope(scope_, GLOBAL_SCOPE);
     info->SetGlobalScope(scope);
-    if (!info->context().is_null()) {
+    if (!info->context().is_null() && !info->context()->IsNativeContext()) {
       scope = Scope::DeserializeScopeChain(*info->context(), scope, zone());
       // The Scope is backed up by ScopeInfo (which is in the V8 heap); this
       // means the Parser cannot operate independent of the V8 heap. Tell the
diff --git a/src/scanner-character-streams.cc b/src/scanner-character-streams.cc
index 23af45fe09..5b30026bef 100644
--- a/src/scanner-character-streams.cc
+++ b/src/scanner-character-streams.cc
@@ -78,7 +78,7 @@ bool BufferedUtf16CharacterStream::ReadBlock() {
     if (buffer_cursor_ < buffer_end_) return true;
     // Otherwise read a new block.
   }
-  unsigned length = FillBuffer(pos_, kBufferSize);
+  unsigned length = FillBuffer(pos_);
   buffer_end_ = buffer_ + length;
   return length > 0;
 }
@@ -118,9 +118,9 @@ unsigned GenericStringUtf16CharacterStream::BufferSeekForward(unsigned delta) {
 }
 
 
-unsigned GenericStringUtf16CharacterStream::FillBuffer(unsigned from_pos,
-                                                      unsigned length) {
+unsigned GenericStringUtf16CharacterStream::FillBuffer(unsigned from_pos) {
   if (from_pos >= length_) return 0;
+  unsigned length = kBufferSize;
   if (from_pos + length > length_) {
     length = length_ - from_pos;
   }
@@ -155,8 +155,7 @@ unsigned Utf8ToUtf16CharacterStream::BufferSeekForward(unsigned delta) {
 }
 
 
-unsigned Utf8ToUtf16CharacterStream::FillBuffer(unsigned char_position,
-                                                unsigned length) {
+unsigned Utf8ToUtf16CharacterStream::FillBuffer(unsigned char_position) {
   static const unibrow::uchar kMaxUtf16Character = 0xffff;
   SetRawPosition(char_position);
   if (raw_character_position_ != char_position) {
@@ -165,7 +164,7 @@ unsigned Utf8ToUtf16CharacterStream::FillBuffer(unsigned char_position,
     return 0u;
   }
   unsigned i = 0;
-  while (i < length - 1) {
+  while (i < kBufferSize - 1) {
     if (raw_data_pos_ == raw_data_length_) break;
     unibrow::uchar c = raw_data_[raw_data_pos_];
     if (c <= unibrow::Utf8::kMaxOneByteChar) {
diff --git a/src/scanner-character-streams.h b/src/scanner-character-streams.h
index a25eb584a5..5297ce897d 100644
--- a/src/scanner-character-streams.h
+++ b/src/scanner-character-streams.h
@@ -29,7 +29,7 @@ class BufferedUtf16CharacterStream: public Utf16CharacterStream {
   virtual void SlowPushBack(uc16 character);
 
   virtual unsigned BufferSeekForward(unsigned delta) = 0;
-  virtual unsigned FillBuffer(unsigned position, unsigned length) = 0;
+  virtual unsigned FillBuffer(unsigned position) = 0;
 
   const uc16* pushback_limit_;
   uc16 buffer_[kBufferSize];
@@ -46,7 +46,7 @@ class GenericStringUtf16CharacterStream: public BufferedUtf16CharacterStream {
 
  protected:
   virtual unsigned BufferSeekForward(unsigned delta);
-  virtual unsigned FillBuffer(unsigned position, unsigned length);
+  virtual unsigned FillBuffer(unsigned position);
 
   Handle<String> string_;
   unsigned length_;
@@ -61,7 +61,7 @@ class Utf8ToUtf16CharacterStream: public BufferedUtf16CharacterStream {
 
  protected:
   virtual unsigned BufferSeekForward(unsigned delta);
-  virtual unsigned FillBuffer(unsigned char_position, unsigned length);
+  virtual unsigned FillBuffer(unsigned char_position);
   void SetRawPosition(unsigned char_position);
 
   const byte* raw_data_;