diff --git a/src/text_file_reader.cpp b/src/text_file_reader.cpp
index f7dc3160d..72db609ac 100644
--- a/src/text_file_reader.cpp
+++ b/src/text_file_reader.cpp
@@ -18,16 +18,19 @@
 
 #include "text_file_reader.h"
 
-#include <libaegisub/io.h>
+#include <libaegisub/file_mapping.h>
+#include <libaegisub/util.h>
 
 #include <algorithm>
 #include <boost/algorithm/string/predicate.hpp>
 #include <boost/algorithm/string/trim.hpp>
+#include <boost/interprocess/streams/bufferstream.hpp>
 
 TextFileReader::TextFileReader(agi::fs::path const& filename, std::string encoding, bool trim)
-: file(agi::io::Open(filename, true))
+: file(agi::util::make_unique<agi::read_file_mapping>(filename))
+, stream(agi::util::make_unique<boost::interprocess::bufferstream>(file->read(0, file->size()), file->size()))
 , trim(trim)
-, iter(agi::line_iterator<std::string>(*file, encoding))
+, iter(agi::line_iterator<std::string>(*stream, encoding))
 {
 }
 
diff --git a/src/text_file_reader.h b/src/text_file_reader.h
index 6b188bce9..4f948a233 100644
--- a/src/text_file_reader.h
+++ b/src/text_file_reader.h
@@ -14,17 +14,20 @@
 //
 // Aegisub Project http://www.aegisub.org/
 
-#include <fstream>
+#include <iosfwd>
 #include <memory>
 #include <string>
 
 #include <libaegisub/fs_fwd.h>
 #include <libaegisub/line_iterator.h>
 
+namespace agi { class read_file_mapping; }
+
 /// @class TextFileReader
 /// @brief A line-based text file reader
 class TextFileReader {
-	std::unique_ptr<std::ifstream> file;
+	std::unique_ptr<agi::read_file_mapping> file;
+	std::unique_ptr<std::istream> stream;
 	bool trim;
 	agi::line_iterator<std::string> iter;