diff --git a/src/filesystem_native.cpp b/src/filesystem_native.cpp
index 1ae415fcdfd..a77bf047c2b 100644
--- a/src/filesystem_native.cpp
+++ b/src/filesystem_native.cpp
@@ -30,7 +30,7 @@
 #include "output.h"
 #include "platform.h"
 
-#ifdef USE_CUSTOM_FILE_READBUF
+#ifdef USE_CUSTOM_FILEBUF
 #  include <sys/stat.h>
 #  include <fcntl.h>
 #endif
@@ -55,14 +55,14 @@ int64_t NativeFilesystem::GetFilesize(StringView path) const {
 }
 
 std::streambuf* NativeFilesystem::CreateInputStreambuffer(StringView path, std::ios_base::openmode mode) const {
-#ifdef USE_CUSTOM_FILE_READBUF
+#ifdef USE_CUSTOM_FILEBUF
 	(void)mode;
 	int fd = open(ToString(path).c_str(), O_RDONLY);
 	if (fd < 0) {
 		return nullptr;
 	}
 
-	return new Filesystem_Stream::FdStreamBuf(fd);
+	return new Filesystem_Stream::FdStreamBuf(fd, true);
 #else
 	auto buf = new std::filebuf();
 
@@ -84,6 +84,20 @@ std::streambuf* NativeFilesystem::CreateInputStreambuffer(StringView path, std::
 }
 
 std::streambuf* NativeFilesystem::CreateOutputStreambuffer(StringView path, std::ios_base::openmode mode) const {
+#ifdef USE_CUSTOM_FILEBUF
+	int flags = O_TRUNC;
+
+	if ((mode & std::ios_base::app) == std::ios_base::app) {
+		flags = O_APPEND;
+	}
+
+	int fd = open(ToString(path).c_str(), O_WRONLY | O_CREAT | flags, S_IRUSR | S_IWUSR);
+	if (fd < 0) {
+		return nullptr;
+	}
+
+	return new Filesystem_Stream::FdStreamBuf(fd, false);
+#else
 	auto* buf = new std::filebuf();
 	buf->open(
 #ifdef _MSC_VER
@@ -99,6 +113,7 @@ std::streambuf* NativeFilesystem::CreateOutputStreambuffer(StringView path, std:
 	}
 
 	return buf;
+#endif
 }
 
 bool NativeFilesystem::GetDirectoryContent(StringView path, std::vector<DirectoryTree::Entry>& entries) const {
diff --git a/src/filesystem_stream.cpp b/src/filesystem_stream.cpp
index 5d20a592497..180a0989587 100644
--- a/src/filesystem_stream.cpp
+++ b/src/filesystem_stream.cpp
@@ -19,7 +19,7 @@
 
 #include <utility>
 
-#ifdef USE_CUSTOM_FILE_READBUF
+#ifdef USE_CUSTOM_FILEBUF
 #  include <unistd.h>
 #endif
 
@@ -127,14 +127,21 @@ Filesystem_Stream::InputMemoryStreamBuf::InputMemoryStreamBuf(std::vector<uint8_
 
 }
 
+#ifdef USE_CUSTOM_FILEBUF
 
-#ifdef USE_CUSTOM_FILE_READBUF
-
-Filesystem_Stream::FdStreamBuf::FdStreamBuf(int fd) : fd(fd) {
-	clear_buffer();
+Filesystem_Stream::FdStreamBuf::FdStreamBuf(int fd, bool is_read) : fd(fd), is_read(is_read) {
+	if (is_read) {
+		clear_buffer();
+	} else {
+		setp(buffer.end(), buffer.end());
+	}
 }
 
 Filesystem_Stream::FdStreamBuf::~FdStreamBuf() {
+	if (!is_read) {
+		sync();
+	}
+
 	close(fd);
 }
 
@@ -152,7 +159,10 @@ Filesystem_Stream::FdStreamBuf::int_type Filesystem_Stream::FdStreamBuf::underfl
 	return traits_type::to_int_type(*gptr());
 }
 
-std::streambuf::pos_type Filesystem_Stream::FdStreamBuf::seekoff(std::streambuf::off_type offset, std::ios_base::seekdir dir, std::ios_base::openmode) {
+std::streambuf::pos_type Filesystem_Stream::FdStreamBuf::seekoff(std::streambuf::off_type offset, std::ios_base::seekdir dir, std::ios_base::openmode mode) {
+	// Not implemented for writing
+	assert(is_read);
+
 	if (dir == std::ios_base::beg) {
 		offset = offset - file_offset + bytes_remaining();
 		dir = std::ios_base::cur;
@@ -199,6 +209,34 @@ std::streambuf::pos_type Filesystem_Stream::FdStreamBuf::seekpos(std::streambuf:
 	return seekoff(pos, std::ios_base::beg, mode);
 }
 
+
+Filesystem_Stream::FdStreamBuf::int_type Filesystem_Stream::FdStreamBuf::overflow(int c) {
+	assert(pptr() == epptr());
+
+	if (c == traits_type::eof() || sync() == -1) {
+		return traits_type::eof();
+	}
+
+	*pptr() = traits_type::to_char_type(c);
+
+	pbump(1);
+	return c;
+}
+
+int Filesystem_Stream::FdStreamBuf::sync() {
+	char *p = pbase();
+	while (p < pptr()) {
+		int written = write(fd, p, pptr() - p);
+		if (written <= 0) {
+			return -1;
+		}
+		p += written;
+	}
+
+	setp(buffer.begin(), buffer.end());
+	return 0;
+}
+
 void Filesystem_Stream::FdStreamBuf::clear_buffer() {
 	setg(buffer.begin(), buffer.end(), buffer.end());
 }
diff --git a/src/filesystem_stream.h b/src/filesystem_stream.h
index 2114f938172..24a1f8b81fe 100644
--- a/src/filesystem_stream.h
+++ b/src/filesystem_stream.h
@@ -97,26 +97,33 @@ namespace Filesystem_Stream {
 		std::vector<uint8_t> buffer;
 	};
 
-#ifdef USE_CUSTOM_FILE_READBUF
+#ifdef USE_CUSTOM_FILEBUF
 	class FdStreamBuf : public std::streambuf {
 	public:
-		FdStreamBuf(int fd);
+		FdStreamBuf(int fd, bool is_read);
 		FdStreamBuf(FdStreamBuf const& other) = delete;
 		FdStreamBuf const& operator=(FdStreamBuf const& other) = delete;
 		~FdStreamBuf();
 
 	protected:
-		int_type underflow();
-		std::streambuf::pos_type seekoff(std::streambuf::off_type offset, std::ios_base::seekdir dir, std::ios_base::openmode mode);
-		std::streambuf::pos_type seekpos(std::streambuf::pos_type pos, std::ios_base::openmode);
+		// Reading
+		int_type underflow() override;
+		std::streambuf::pos_type seekoff(std::streambuf::off_type offset, std::ios_base::seekdir dir, std::ios_base::openmode mode) override;
+		std::streambuf::pos_type seekpos(std::streambuf::pos_type pos, std::ios_base::openmode) override;
 
+		// Writing
+		int_type overflow(int c = EOF) override;
+		int sync() override;
 	private:
+		// Reading
 		void clear_buffer();
 		ssize_t bytes_remaining() const;
+		off_t file_offset = 0;
 
+		// Both
 		int fd;
-		off_t file_offset = 0;
-		std::array<char, USE_CUSTOM_FILE_READBUF> buffer;
+		bool is_read; // Streams can be read and write but we only always use one mode
+		std::array<char, USE_CUSTOM_FILEBUF> buffer;
 	};
 #endif
 
diff --git a/src/system.h b/src/system.h
index 012a5a16215..05c1aabafc5 100644
--- a/src/system.h
+++ b/src/system.h
@@ -60,21 +60,21 @@
 #elif defined(__3DS__)
 #  define SUPPORT_JOYSTICK
 #  define SUPPORT_JOYSTICK_AXIS
-#  define USE_CUSTOM_FILE_READBUF 4 * 1024
+#  define USE_CUSTOM_FILEBUF 4 * 1024
 #elif defined(__vita__)
 #  define SUPPORT_JOYSTICK
 #  define SUPPORT_JOYSTICK_AXIS
-#  define USE_CUSTOM_FILE_READBUF 4 * 1024
+#  define USE_CUSTOM_FILEBUF 4 * 1024
 #elif defined(__wii__)
 #  include <cstdint>
 #  define SUPPORT_JOYSTICK
 #  define SUPPORT_JOYSTICK_AXIS
-#  define USE_CUSTOM_FILE_READBUF 4 * 1024
+#  define USE_CUSTOM_FILEBUF 4 * 1024
 #elif defined(__WIIU__)
 #  define SUPPORT_JOYSTICK
 #  define SUPPORT_JOYSTICK_AXIS
 #  define SUPPORT_TOUCH
-#  define USE_CUSTOM_FILE_READBUF 16 * 1024
+#  define USE_CUSTOM_FILEBUF 16 * 1024
 #elif defined(_WIN32)
 #  define SUPPORT_ZOOM
 #  define SUPPORT_MOUSE
@@ -84,7 +84,7 @@
 #elif defined(__SWITCH__)
 #  define SUPPORT_JOYSTICK
 #  define SUPPORT_JOYSTICK_AXIS
-#  define USE_CUSTOM_FILE_READBUF 16 * 1024
+#  define USE_CUSTOM_FILEBUF 16 * 1024
 #elif defined(PLAYER_AMIGA) && !defined(__AROS__)
 #  define SUPPORT_ZOOM
 #  define SUPPORT_MOUSE