diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index 2345cb0ab88..007837ebf5e 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -1348,6 +1348,7 @@ void QXcbWindow::setWindowIconText(const QString &title)
 void QXcbWindow::setWindowIcon(const QIcon &icon)
 {
     QList<quint32> icon_data;
+    const uint32_t sizeLimit = xcb_get_maximum_request_length(xcb_connection());
     if (!icon.isNull()) {
         QList<QSize> availableSizes = icon.availableSizes();
         if (availableSizes.isEmpty()) {
@@ -1363,7 +1364,12 @@ void QXcbWindow::setWindowIcon(const QIcon &icon)
             if (!pixmap.isNull()) {
                 QImage image = pixmap.toImage().convertToFormat(QImage::Format_ARGB32);
                 int pos = icon_data.size();
-                icon_data.resize(pos + 2 + image.width()*image.height());
+                int newSize = pos + 2 + image.width()*image.height();
+                // In the absence of the BIG-REQUESTS extension, or with too big DPR,
+                // the size of icon data is too big for the xcb request very easily.
+                if (quint64(newSize) > quint64(sizeLimit))
+                    break;
+                icon_data.resize(newSize);
                 icon_data[pos++] = image.width();
                 icon_data[pos++] = image.height();
                 memcpy(icon_data.data() + pos, image.bits(), image.width()*image.height()*4);
@@ -1373,10 +1379,10 @@ void QXcbWindow::setWindowIcon(const QIcon &icon)
 
     if (!icon_data.isEmpty()) {
         // Ignore icon exceeding maximum xcb request length
-        if (quint64(icon_data.size()) > quint64(xcb_get_maximum_request_length(xcb_connection()))) {
+        if (quint64(icon_data.size()) > quint64(sizeLimit)) {
             qWarning() << "Ignoring window icon" << icon_data.size()
                        << "exceeds maximum xcb request length"
-                       << xcb_get_maximum_request_length(xcb_connection());
+                       << sizeLimit;
             return;
         }
         xcb_change_property(xcb_connection(),