diff --git a/src/plugins/designer/qtcreatorintegration.cpp b/src/plugins/designer/qtcreatorintegration.cpp
index 421854a3644..f756c8c1969 100644
--- a/src/plugins/designer/qtcreatorintegration.cpp
+++ b/src/plugins/designer/qtcreatorintegration.cpp
@@ -68,6 +68,7 @@
 #include <QtGui/QMessageBox>
 
 #include <QtCore/QFileInfo>
+#include <QtCore/QDir>
 #include <QtCore/QDebug>
 #include <QtCore/QUrl>
 
@@ -81,11 +82,13 @@ static QString msgClassNotFound(const QString &uiClassName, const QList<Document
 {
     QString files;
     foreach (const Document::Ptr &doc, docList) {
-        if (!files.isEmpty())
-            files += QLatin1String(", ");
-        files += doc->fileName();
+        files += QLatin1Char('\n');
+        files += QDir::toNativeSeparators(doc->fileName());
     }
-    return QtCreatorIntegration::tr("The class definition of '%1' could not be found in %2.").arg(uiClassName, files);
+    return QtCreatorIntegration::tr(
+        "The class containing '%1' could not be found in %2.\n"
+        "Please verify the #include-directives.")
+        .arg(uiClassName, files);
 }
 
 QtCreatorIntegration::QtCreatorIntegration(QDesignerFormEditorInterface *core, FormEditorW *parent) :