diff --git a/xembed-sni-proxy/sniproxy.cpp b/xembed-sni-proxy/sniproxy.cpp
--- a/xembed-sni-proxy/sniproxy.cpp
+++ b/xembed-sni-proxy/sniproxy.cpp
@@ -288,7 +288,13 @@
     xcb_image_t *image = xcb_image_get(c, m_windowId, 0, 0, geom->width, geom->height, 0xFFFFFFFF, XCB_IMAGE_FORMAT_Z_PIXMAP);
 
     // Don't hook up cleanup yet, we may use a different QImage after all
-    QImage naiveConversion = QImage(image->data, image->width, image->height, QImage::Format_ARGB32);
+    QImage naiveConversion;
+    if (image) {
+        naiveConversion = QImage(image->data, image->width, image->height, QImage::Format_ARGB32);
+    } else {
+        qCDebug(SNIPROXY) << "Skip NULL image returned from xcb_image_get() for" << m_windowId << Title();
+        return QImage();
+    }
 
     if (isTransparentImage(naiveConversion)) {
         QImage elaborateConversion = QImage(convertFromNative(image));