diff --git a/src/gui/text/qtextlayout.cpp b/src/gui/text/qtextlayout.cpp
index 2a8d4605b0f..cab9f6ae612 100644
--- a/src/gui/text/qtextlayout.cpp
+++ b/src/gui/text/qtextlayout.cpp
@@ -2091,7 +2091,9 @@ static QGlyphRun glyphRunWithInfo(QFontEngine *fontEngine,
     qreal minY = 0;
     qreal maxY = 0;
     QVector<quint32> glyphs;
+    glyphs.reserve(glyphsArray.size());
     QVector<QPointF> positions;
+    positions.reserve(glyphsArray.size());
     for (int i=0; i<glyphsArray.size(); ++i) {
         glyphs.append(glyphsArray.at(i) & 0xffffff);