diff --git a/src/gui/CMakeLists.txt b/src/gui/CMakeLists.txt
index c93a923fe8b..6e858e85cc4 100644
--- a/src/gui/CMakeLists.txt
+++ b/src/gui/CMakeLists.txt
@@ -335,8 +335,8 @@ if(QT_FEATURE_pdf)
     )
 endif()
 
-if(WIN32 OR (UNIX AND NOT APPLE))
-    set_target_properties(Gui PROPERTIES UNITY_BUILD OFF) # X11 define clashes/Windows oddities.
+if(UNIX AND NOT APPLE)
+    set_target_properties(Gui PROPERTIES UNITY_BUILD OFF) # X11 define clashes.
 endif()
 
 qt_internal_add_resource(Gui "gui_shaders"
@@ -491,6 +491,8 @@ qt_internal_extend_target(Gui CONDITION WIN32
         dxgi
         dxguid
         d3d12
+    NO_UNITY_BUILD_SOURCES
+        text/windows/qwindowsfontdatabasebase.cpp # duplicate struct OS2Table
     ATTRIBUTION_FILE_DIR_PATHS
         ../3rdparty/D3D12MemoryAllocator
 )
diff --git a/src/gui/painting/qpagelayout.cpp b/src/gui/painting/qpagelayout.cpp
index a913f6fef75..e6f346dcdf2 100644
--- a/src/gui/painting/qpagelayout.cpp
+++ b/src/gui/painting/qpagelayout.cpp
@@ -37,7 +37,7 @@ Q_GUI_EXPORT qreal qt_pointMultiplier(QPageLayout::Unit unit)
 }
 
 // Multiplier for converting pixels to points.
-extern qreal qt_pixelMultiplier(int resolution);
+Q_GUI_EXPORT extern qreal qt_pixelMultiplier(int resolution);
 
 Q_GUI_EXPORT QMarginsF qt_convertMargins(const QMarginsF &margins, QPageLayout::Unit fromUnits, QPageLayout::Unit toUnits)
 {
diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index 344bb8f1bef..914eb2fe407 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -2588,7 +2588,7 @@ QRegion QPainter::clipRegion() const
     return region;
 }
 
-extern QPainterPath qt_regionToPath(const QRegion &region);
+Q_GUI_EXPORT extern QPainterPath qt_regionToPath(const QRegion &region);
 
 /*!
     Returns the current clip path in logical coordinates.
diff --git a/src/gui/painting/qpdf.cpp b/src/gui/painting/qpdf.cpp
index db289460260..6419ef64435 100644
--- a/src/gui/painting/qpdf.cpp
+++ b/src/gui/painting/qpdf.cpp
@@ -1215,8 +1215,6 @@ void QPdfEngine::setupGraphicsState(QPaintEngine::DirtyFlags flags)
         setPen();
 }
 
-extern QPainterPath qt_regionToPath(const QRegion &region);
-
 void QPdfEngine::updateClipPath(const QPainterPath &p, Qt::ClipOperation op)
 {
     Q_D(QPdfEngine);
diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 40b213c5047..eaa836bff90 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -1325,7 +1325,7 @@ QPolygon QTransform::map(const QPolygon &a) const
     \sa QTransform::map()
 */
 
-extern QPainterPath qt_regionToPath(const QRegion &region);
+Q_GUI_EXPORT extern QPainterPath qt_regionToPath(const QRegion &region);
 
 /*!
     \fn QRegion QTransform::map(const QRegion &region) const
diff --git a/src/printsupport/kernel/qprinter.cpp b/src/printsupport/kernel/qprinter.cpp
index fcbb52661b7..cc95c97344a 100644
--- a/src/printsupport/kernel/qprinter.cpp
+++ b/src/printsupport/kernel/qprinter.cpp
@@ -39,7 +39,7 @@ using namespace Qt::StringLiterals;
         return retValue; \
     }
 
-extern qreal qt_pixelMultiplier(int resolution);
+Q_GUI_EXPORT extern qreal qt_pixelMultiplier(int resolution);
 extern QMarginsF qt_convertMargins(const QMarginsF &margins, QPageLayout::Unit fromUnits, QPageLayout::Unit toUnits);
 
 QPrinterInfo QPrinterPrivate::findValidPrinter(const QPrinterInfo &printer)
diff --git a/src/widgets/graphicsview/qgraphicsitem.cpp b/src/widgets/graphicsview/qgraphicsitem.cpp
index a06de022b85..d6c06ac8636 100644
--- a/src/widgets/graphicsview/qgraphicsitem.cpp
+++ b/src/widgets/graphicsview/qgraphicsitem.cpp
@@ -9313,7 +9313,7 @@ QVariant QGraphicsLineItem::extension(const QVariant &variant) const
     QPixmap::createHeuristicMask().  The performance and memory consumption
     is similar to MaskShape.
 */
-extern QPainterPath qt_regionToPath(const QRegion &region);
+Q_GUI_EXPORT extern QPainterPath qt_regionToPath(const QRegion &region);
 
 class QGraphicsPixmapItemPrivate : public QGraphicsItemPrivate
 {
diff --git a/src/widgets/graphicsview/qgraphicsview.cpp b/src/widgets/graphicsview/qgraphicsview.cpp
index 54065e8e580..60ccdc15a89 100644
--- a/src/widgets/graphicsview/qgraphicsview.cpp
+++ b/src/widgets/graphicsview/qgraphicsview.cpp
@@ -1115,7 +1115,7 @@ void QGraphicsViewPrivate::freeStyleOptionsArray(QStyleOptionGraphicsItem *array
         delete [] array;
 }
 
-extern QPainterPath qt_regionToPath(const QRegion &region);
+Q_GUI_EXPORT extern QPainterPath qt_regionToPath(const QRegion &region);
 
 /*!
     ### Adjustments in findItems: mapToScene(QRect) forces us to adjust the