diff --git a/src/solid/devices/backends/udisks2/udisksdevicebackend.cpp b/src/solid/devices/backends/udisks2/udisksdevicebackend.cpp
--- a/src/solid/devices/backends/udisks2/udisksdevicebackend.cpp
+++ b/src/solid/devices/backends/udisks2/udisksdevicebackend.cpp
@@ -140,6 +140,13 @@
 
         if (reply.isValid()) {
             auto props = reply.value();
+            if (iface == QStringLiteral(UD2_DBUS_INTERFACE_FILESYSTEM)) {
+                // UDisks2 2.7.6 added a Size property for Filesystem, which uses 0 for unknown
+                auto size = props.take(QStringLiteral("Size"));
+                if (size.isValid() && size.toInt() != 0) {
+                    m_propertyCache.insert(QStringLiteral("Size"), size);
+                }
+            }
             // Can not use QMap<>::unite(), as it allows multiple values per key
             for (auto it = props.cbegin(); it != props.cend(); ++it) {
                 m_propertyCache.insert(it.key(), it.value());