diff --git a/src/common/file_stream.h b/src/common/file_stream.h
index 9abe7e23..7f5236f7 100755
--- a/src/common/file_stream.h
+++ b/src/common/file_stream.h
@@ -178,11 +178,9 @@ public:
   bool empty() { return istream_->peek() == std::ifstream::traits_type::eof(); }
 
   void setbufsize(size_t size) const {
-#ifdef 0 // this is buggy, do nothing
     istream_->rdbuf()->pubsetbuf(0, 0);
-    readBuf_.reset(new char[size]);
-    istream_->rdbuf()->pubsetbuf(readBuf_.get(), 0);
-#endif
+    readBuf_.resize(size);
+    istream_->rdbuf()->pubsetbuf(readBuf_.data(), readBuf_.size());
   }
 
   template <typename T>
@@ -206,9 +204,10 @@ private:
   std::unique_ptr<std::istream> istream_;
 
   boost::iostreams::file_descriptor_source fds_;
+  mutable std::vector<char> readBuf_; // for setbuf()
   std::unique_ptr<boost::iostreams::stream_buffer<boost::iostreams::file_descriptor_source>> fdsBuffer_;
 
-  mutable UPtr<char[]> readBuf_; // for setbuf()
+
 };
 
 // wrapper around std::getline() that handles Windows input files with extra CR
@@ -301,6 +300,7 @@ private:
   marian::filesystem::Path file_;
   std::unique_ptr<std::ostream> ostream_;
 
+
   boost::iostreams::file_descriptor_sink fds_;
   std::unique_ptr<boost::iostreams::stream_buffer<boost::iostreams::file_descriptor_sink>> fdsBuffer_;
 };