diff --git a/Telegram/Patches/qtbase_5_6_2.diff b/Telegram/Patches/qtbase_5_6_2.diff
index 5bd013a69..4961a5bc8 100644
--- a/Telegram/Patches/qtbase_5_6_2.diff
+++ b/Telegram/Patches/qtbase_5_6_2.diff
@@ -16,6 +16,25 @@ index eec9e1f..7ae53c7 100644
  QMAKE_CFLAGS_YACC       =
  QMAKE_CFLAGS_LTCG       = -GL
  QMAKE_CFLAGS_SSE2       = -arch:SSE2
+diff --git a/src/corelib/io/qfsfileengine_win.cpp b/src/corelib/io/qfsfileengine_win.cpp
+index 391fbcc..d07802b 100644
+--- a/src/corelib/io/qfsfileengine_win.cpp
++++ b/src/corelib/io/qfsfileengine_win.cpp
+@@ -427,11 +427,12 @@ qint64 QFSFileEnginePrivate::nativeWrite(const char *data, qint64 len)
+ 
+     // Writing on Windows fails with ERROR_NO_SYSTEM_RESOURCES when
+     // the chunks are too large, so we limit the block size to 32MB.
+-    const DWORD blockSize = DWORD(qMin(bytesToWrite, qint64(32 * 1024 * 1024)));
+     qint64 totalWritten = 0;
+     do {
++        // Patch: backport critical bugfix from '683c9bc4a8' commit.
++        const DWORD currentBlockSize = DWORD(qMin(bytesToWrite, qint64(32 * 1024 * 1024)));
+         DWORD bytesWritten;
+-        if (!WriteFile(fileHandle, data + totalWritten, blockSize, &bytesWritten, NULL)) {
++        if (!WriteFile(fileHandle, data + totalWritten, currentBlockSize, &bytesWritten, NULL)) {
+             if (totalWritten == 0) {
+                 // Note: Only return error if the first WriteFile failed.
+                 q->setError(QFile::WriteError, qt_error_string());
 diff --git a/src/corelib/tools/qunicodetables.cpp b/src/corelib/tools/qunicodetables.cpp
 index 14e4fd1..0619a17 100644
 --- a/src/corelib/tools/qunicodetables.cpp
diff --git a/Telegram/Resources/art/bg_initial.jpg b/Telegram/Resources/art/bg_initial.jpg
new file mode 100644
index 000000000..602b52834
Binary files /dev/null and b/Telegram/Resources/art/bg_initial.jpg differ
diff --git a/Telegram/Resources/art/bg_initial.png b/Telegram/Resources/art/bg_initial.png
deleted file mode 100644
index 8c5073a61..000000000
Binary files a/Telegram/Resources/art/bg_initial.png and /dev/null differ
diff --git a/Telegram/Resources/telegram.qrc b/Telegram/Resources/telegram.qrc
index 6fece6a45..e1db7041b 100644
--- a/Telegram/Resources/telegram.qrc
+++ b/Telegram/Resources/telegram.qrc
@@ -5,7 +5,7 @@
     <file>art/fonts/OpenSans-Semibold.ttf</file>
     <file>art/newmsg.wav</file>
     <file>art/bg.jpg</file>
-    <file>art/bg_initial.png</file>
+    <file>art/bg_initial.jpg</file>
     <file>art/icon256.png</file>
     <file>art/iconbig256.png</file>
     <file>art/sunrise.jpg</file>
diff --git a/Telegram/SourceFiles/boxes/backgroundbox.cpp b/Telegram/SourceFiles/boxes/backgroundbox.cpp
index 6a3e2d5a9..f60637249 100644
--- a/Telegram/SourceFiles/boxes/backgroundbox.cpp
+++ b/Telegram/SourceFiles/boxes/backgroundbox.cpp
@@ -76,7 +76,7 @@ BackgroundBox::Inner::Inner(QWidget *parent) : TWidget(parent)
 void BackgroundBox::Inner::gotWallpapers(const MTPVector<MTPWallPaper> &result) {
 	App::WallPapers wallpapers;
 
-	auto oldBackground = ImagePtr(qsl(":/gui/art/bg_initial.png"));
+	auto oldBackground = ImagePtr(qsl(":/gui/art/bg_initial.jpg"));
 	wallpapers.push_back(App::WallPaper(Window::Theme::kInitialBackground, oldBackground, oldBackground));
 	auto &v = result.c_vector().v;
 	for_const (auto &w, v) {
diff --git a/Telegram/SourceFiles/window/window_theme.cpp b/Telegram/SourceFiles/window/window_theme.cpp
index ff14508c5..a9c9cb016 100644
--- a/Telegram/SourceFiles/window/window_theme.cpp
+++ b/Telegram/SourceFiles/window/window_theme.cpp
@@ -400,7 +400,7 @@ void ChatBackground::setImage(int32 id, QImage &&image) {
 		setPreparedImage(std_::move(image));
 	} else {
 		if (_id == kInitialBackground) {
-			image.load(qsl(":/gui/art/bg_initial.png"));
+			image.load(qsl(":/gui/art/bg_initial.jpg"));
 			if (cRetina()) {
 				image = image.scaledToWidth(image.width() * 2, Qt::SmoothTransformation);
 			} else if (cScale() != dbisOne) {