diff --git a/src/google/protobuf/util/json_util.cc b/src/google/protobuf/util/json_util.cc
index d7ac2dba66..5974cc4aa3 100644
--- a/src/google/protobuf/util/json_util.cc
+++ b/src/google/protobuf/util/json_util.cc
@@ -49,22 +49,25 @@ namespace protobuf {
 namespace util {
 
 namespace internal {
+ZeroCopyStreamByteSink::~ZeroCopyStreamByteSink() {
+  stream_->BackUp(buffer_size_);
+}
+
 void ZeroCopyStreamByteSink::Append(const char* bytes, size_t len) {
-  while (len > 0) {
-    void* buffer;
-    int length;
-    if (!stream_->Next(&buffer, &length)) {
-      // There isn't a way for ByteSink to report errors.
+  while (true) {
+    if (len <= buffer_size_) {
+      memcpy(buffer_, bytes, len);
+      buffer_ = static_cast<char*>(buffer_) + len;
+      buffer_size_ -= len;
       return;
     }
-    if (len < length) {
-      memcpy(buffer, bytes, len);
-      stream_->BackUp(length - len);
-      break;
-    } else {
-      memcpy(buffer, bytes, length);
-      bytes += length;
-      len -= length;
+    memcpy(buffer_, bytes, buffer_size_);
+    bytes += buffer_size_;
+    len -= buffer_size_;
+    if (!stream_->Next(&buffer_, &buffer_size_)) {
+      // There isn't a way for ByteSink to report errors.
+      buffer_size_ = 0;
+      return;
     }
   }
 }
diff --git a/src/google/protobuf/util/json_util.h b/src/google/protobuf/util/json_util.h
index 6d3cee5281..0e45ef810a 100644
--- a/src/google/protobuf/util/json_util.h
+++ b/src/google/protobuf/util/json_util.h
@@ -172,12 +172,15 @@ namespace internal {
 class LIBPROTOBUF_EXPORT ZeroCopyStreamByteSink : public strings::ByteSink {
  public:
   explicit ZeroCopyStreamByteSink(io::ZeroCopyOutputStream* stream)
-      : stream_(stream) {}
+      : stream_(stream), buffer_size_(0) {}
+  ~ZeroCopyStreamByteSink();
 
   virtual void Append(const char* bytes, size_t len);
 
  private:
   io::ZeroCopyOutputStream* stream_;
+  void* buffer_;
+  int buffer_size_;
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ZeroCopyStreamByteSink);
 };