Index: /trunk/src/VBox/Frontends/VirtualBox/src/medium/UIMediumDetailsWidget.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/medium/UIMediumDetailsWidget.cpp	(revision 68326)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/medium/UIMediumDetailsWidget.cpp	(revision 68327)
@@ -670,5 +670,5 @@
     {
         /* Always valid for now: */
-        const bool fError = false;
+        const bool fError = m_newData.m_options.m_uLogicalSize < m_oldData.m_options.m_uLogicalSize;
         m_pErrorPaneSize->setVisible(fError);
         if (fError)
@@ -680,5 +680,5 @@
 }
 
-void UIMediumDetailsWidget::retranslateValidation(QWidget * /* pWidget = 0 */)
+void UIMediumDetailsWidget::retranslateValidation(QWidget *pWidget /* = 0 */)
 {
     /* Translate 'Interface' tab content: */
@@ -692,7 +692,7 @@
 //        m_pErrorPaneDescription->setToolTip(tr("Cannot change medium description from <b>%1</b> to <b>%2</b>.")
 //                                               .arg(m_oldData.m_options.m_strDescription).arg(m_newData.m_options.m_strDescription));
-//    if (!pWidget || pWidget == m_pErrorPaneSize)
-//        m_pErrorPaneSize->setToolTip(tr("Cannot change medium size from <b>%1</b> to <b>%2</b>.")
-//                                         .arg(m_oldData.m_options.m_uLogicalSize).arg(m_newData.m_options.m_uLogicalSize));
+    if (!pWidget || pWidget == m_pErrorPaneSize)
+        m_pErrorPaneSize->setToolTip(tr("Cannot change medium size from <b>%1</b> to <b>%2</b> as storage shrinking is currently forbidden.")
+                                         .arg(m_oldData.m_options.m_uLogicalSize).arg(m_newData.m_options.m_uLogicalSize));
 }