diff --git a/src/core/batchrenamejob.cpp b/src/core/batchrenamejob.cpp
--- a/src/core/batchrenamejob.cpp
+++ b/src/core/batchrenamejob.cpp
@@ -59,9 +59,8 @@
 
         // Check for extensions.
         QSet<QString> extensions;
-        QMimeDatabase db;
         foreach (const QUrl &url, m_srcList) {
-            const QString extension = db.suffixForFileName(url.toDisplayString().toLower());
+	    const QString extension = fileExtension(url.fileName());
             if (extensions.contains(extension)) {
                 m_allExtensionsDifferent = false;
                 break;
@@ -102,6 +101,7 @@
     Q_DECLARE_PUBLIC(BatchRenameJob)
 
     void slotStart();
+    static QString fileExtension(const QString& filename);
 
     QString indexedName(const QString& name, int index, QChar placeHolder) const;
 
@@ -157,6 +157,26 @@
     return newName;
 }
 
+// The function QMimeDatabase.suffixForFileName always converts the extension to lower case
+// This function is a helper which avoids the conversion to lower case
+QString BatchRenameJobPrivate::fileExtension(const QString& filename)
+{
+    QMimeDatabase db;
+    const size_t extensionLen = db.suffixForFileName(filename).length();
+     
+    //extensionLen will be 0 if the extension is not in the QMimeDatabase i.e "foo.xyz"
+    if (extensionLen) {
+        return filename.right(extensionLen);
+    } else {
+        //Fallback to everything right of the last '.'
+        const int dotIndex = filename.lastIndexOf(QStringLiteral("."));
+        if (dotIndex != -1) {
+            return filename.mid(dotIndex+1);
+        }
+    }
+    return QStringLiteral();
+}
+
 void BatchRenameJobPrivate::slotStart()
 {
     Q_Q(BatchRenameJob);
@@ -168,8 +188,7 @@
     if (m_listIterator != m_srcList.constEnd()) {
         QString newName = indexedName(m_newName, m_index, m_placeHolder);
         const QUrl oldUrl = *m_listIterator;
-        QMimeDatabase db;
-        const QString extension = db.suffixForFileName(oldUrl.path().toLower());
+        const QString extension = fileExtension(oldUrl.fileName());
         if (!extension.isEmpty()) {
             newName += QLatin1Char('.') + extension;
         }