diff --git a/qt5-serialport/mingw-w64/0001-Revert-Emit-_q_notify-only-if-there-s-no-notificatio.patch b/qt5-serialport/mingw-w64/0001-Revert-Emit-_q_notify-only-if-there-s-no-notificatio.patch
new file mode 100644
index 00000000..9e32c273
--- /dev/null
+++ b/qt5-serialport/mingw-w64/0001-Revert-Emit-_q_notify-only-if-there-s-no-notificatio.patch
@@ -0,0 +1,57 @@
+From 878bb0fc614f83757b69ba7665babc7fc7d56b01 Mon Sep 17 00:00:00 2001
+From: Denis Shienkov <denis.shienkov@gmail.com>
+Date: Fri, 6 Sep 2019 21:19:52 +0300
+Subject: [PATCH] Revert "Emit _q_notify only if there's no notification
+ pending"
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This reverts commit 85ee2c658a45d2958a54045951d236769640337f.
+
+That commit completely breaks the I/O on Windows.
+
+Task-number: QTBUG-78086
+Change-Id: I6c6b8ef0b5af7bd9dcbea791fbb8322c9e68b900
+Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
+(cherry picked from commit f6b43c36b3839dae54308a6437bbdd99ae9a44de)
+---
+ src/serialport/qwinoverlappedionotifier.cpp | 10 +++-------
+ 1 file changed, 3 insertions(+), 7 deletions(-)
+
+diff --git a/src/serialport/qwinoverlappedionotifier.cpp b/src/serialport/qwinoverlappedionotifier.cpp
+index 233ee69..615dacc 100644
+--- a/src/serialport/qwinoverlappedionotifier.cpp
++++ b/src/serialport/qwinoverlappedionotifier.cpp
+@@ -129,7 +129,6 @@ public:
+     HANDLE hSemaphore = nullptr;
+     HANDLE hResultsMutex = nullptr;
+     QAtomicInt waiting;
+-    QAtomicInt pendingNotifications;
+     QQueue<IOResult> results;
+ };
+ 
+@@ -396,17 +395,14 @@ void QWinOverlappedIoNotifierPrivate::notify(DWORD numberOfBytes, DWORD errorCod
+     results.enqueue(IOResult(numberOfBytes, errorCode, overlapped));
+     ReleaseMutex(hResultsMutex);
+     ReleaseSemaphore(hSemaphore, 1, NULL);
+-    if (!waiting && pendingNotifications-- == 0)
++    if (!waiting)
+         emit q->_q_notify();
+ }
+ 
+ void QWinOverlappedIoNotifierPrivate::_q_notified()
+ {
+-    int n = pendingNotifications.fetchAndStoreAcquire(0);
+-    while (--n >= 0) {
+-        if (WaitForSingleObject(hSemaphore, 0) == WAIT_OBJECT_0)
+-            dispatchNextIoResult();
+-    }
++    if (WaitForSingleObject(hSemaphore, 0) == WAIT_OBJECT_0)
++        dispatchNextIoResult();
+ }
+ 
+ OVERLAPPED *QWinOverlappedIoNotifierPrivate::dispatchNextIoResult()
+-- 
+2.23.0
+
diff --git a/qt5-serialport/mingw-w64/PKGBUILD b/qt5-serialport/mingw-w64/PKGBUILD
index 1863c84d..7caa97f5 100644
--- a/qt5-serialport/mingw-w64/PKGBUILD
+++ b/qt5-serialport/mingw-w64/PKGBUILD
@@ -10,7 +10,7 @@
 _qt_module=qtserialport
 pkgname="mingw-w64-qt5-serialport"
 pkgver=5.13.1
-pkgrel=1
+pkgrel=2
 arch=('any')
 pkgdesc="Provides access to hardware and virtual serial ports (mingw-w64)"
 depends=('mingw-w64-qt5-base')
@@ -20,8 +20,10 @@ groups=('mingw-w64-qt5')
 license=('GPL3' 'LGPL3' 'FDL' 'custom')
 url='https://www.qt.io/'
 _pkgfqn="${_qt_module}-everywhere-src-$pkgver"
-source=("https://download.qt.io/official_releases/qt/${pkgver%.*}/$pkgver/submodules/${_pkgfqn}.tar.xz")
-sha256sums=('d96706f406d89b459ed0ecd129b68309a91cea0f132b839958b5311ea0d118d2')
+source=("https://download.qt.io/official_releases/qt/${pkgver%.*}/$pkgver/submodules/${_pkgfqn}.tar.xz"
+        '0001-Revert-Emit-_q_notify-only-if-there-s-no-notificatio.patch')
+sha256sums=('d96706f406d89b459ed0ecd129b68309a91cea0f132b839958b5311ea0d118d2'
+            '93f027427ebde7ecd969b0ddca9526fbea0c4524cc4b62b31ce6d0b7a2693e52')
 
 _architectures='i686-w64-mingw32 x86_64-w64-mingw32'
 [[ $NO_STATIC_LIBS ]] || \
@@ -33,8 +35,14 @@ _architectures='i686-w64-mingw32 x86_64-w64-mingw32'
 
 prepare() {
   cd "${srcdir}/${_pkgfqn}"
-  # Don't build examples or tests.
+
+  # don't build examples or tests.
   sed -i 's/ examples tests//' qtserialport.pro
+
+  # apply patches; further descriptions can be found in patch files itself
+  for patch in "$srcdir/"*.patch; do
+    patch -p1 -i "$patch"
+  done
 }
 
 build() {