diff -up qt-everywhere-opensource-src-4.8.7/src/svg/qsvgfont_p.h.me qt-everywhere-opensource-src-4.8.7/src/svg/qsvgfont_p.h
--- qt-everywhere-opensource-src-4.8.7/src/svg/qsvgfont_p.h.me	2023-05-18 14:45:36.239081107 +0200
+++ qt-everywhere-opensource-src-4.8.7/src/svg/qsvgfont_p.h	2023-05-18 14:47:11.440869275 +0200
@@ -78,6 +78,7 @@ public:
 class QSvgFont : public QSvgRefCounted
 {
 public:
+    static const qreal DEFAULT_UNITS_PER_EM = 1000;
     QSvgFont(qreal horizAdvX);
 
     void setFamilyName(const QString &name);
@@ -90,9 +91,7 @@ public:
     void draw(QPainter *p, const QPointF &point, const QString &str, qreal pixelSize, Qt::Alignment alignment) const;
 public:
     QString m_familyName;
-    qreal m_unitsPerEm;
-    qreal m_ascent;
-    qreal m_descent;
+    qreal m_unitsPerEm = DEFAULT_UNITS_PER_EM;
     qreal m_horizAdvX;
     QHash<QChar, QSvgGlyph> m_glyphs;
 };
diff -up qt-everywhere-opensource-src-4.8.7/src/svg/qsvghandler.cpp.me qt-everywhere-opensource-src-4.8.7/src/svg/qsvghandler.cpp
--- qt-everywhere-opensource-src-4.8.7/src/svg/qsvghandler.cpp.me	2023-05-18 14:45:24.569107055 +0200
+++ qt-everywhere-opensource-src-4.8.7/src/svg/qsvghandler.cpp	2023-05-18 14:45:10.885137479 +0200
@@ -2571,7 +2571,7 @@ static bool parseFontFaceNode(QSvgStyleP
 
     qreal unitsPerEm = toDouble(unitsPerEmStr);
     if (!unitsPerEm)
-        unitsPerEm = 1000;
+        unitsPerEm = QSvgFont::DEFAULT_UNITS_PER_EM;
 
     if (!name.isEmpty())
         font->setFamilyName(name);