diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index 38a448fd0cd..c1024fdbec0 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,20 @@
+2012-11-22  Allan Sandfeld Jensen  <allan.jensen@digia.com>
+
+        [Qt] Correct extensions on preferredFilename
+        https://bugs.webkit.org/show_bug.cgi?id=103054
+
+        Reviewed by Simon Hausmann.
+
+        When guessing a filename we will now ensure it has an extension that is valid for its mimetype.
+        To do this the two missing methods getExtensionsForMIMEType and getPreferredExtensionForMIMEType
+        have been added to the Qt implementation of MIMETypeRegistry.
+
+        * platform/network/qt/QNetworkReplyHandler.cpp:
+        (WebCore::QNetworkReplyHandler::sendResponseIfNeeded):
+        * platform/qt/MIMETypeRegistryQt.cpp:
+        (WebCore::MIMETypeRegistry::getExtensionsForMIMEType):
+        (WebCore::MIMETypeRegistry::getPreferredExtensionForMIMEType):
+
 2012-11-22  Kent Tamura  <tkent@chromium.org>
 
         INPUT_MULTIPLE_FIELDS_UI: Refactoring: Do not call updateInnerTextValue if only read-only sub-fields have values
diff --git a/Source/WebCore/platform/network/qt/QNetworkReplyHandler.cpp b/Source/WebCore/platform/network/qt/QNetworkReplyHandler.cpp
index b83f2ba08c2..904e859831d 100644
--- a/Source/WebCore/platform/network/qt/QNetworkReplyHandler.cpp
+++ b/Source/WebCore/platform/network/qt/QNetworkReplyHandler.cpp
@@ -32,6 +32,7 @@
 #include <QDateTime>
 #include <QFile>
 #include <QFileInfo>
+#include <QMimeDatabase>
 #include <QNetworkCookie>
 #include <QNetworkReply>
 
@@ -581,8 +582,21 @@ void QNetworkReplyHandler::sendResponseIfNeeded()
 
         if (!suggestedFilename.isEmpty())
             response.setSuggestedFilename(suggestedFilename);
-        else
-            response.setSuggestedFilename(url.lastPathComponent());
+        else {
+            Vector<String> extensions = MIMETypeRegistry::getExtensionsForMIMEType(mimeType);
+            if (extensions.isEmpty())
+                response.setSuggestedFilename(url.lastPathComponent());
+            else {
+                // If the suffix doesn't match the MIME type, correct the suffix.
+                QString filename = url.lastPathComponent();
+                const String suffix = QMimeDatabase().suffixForFileName(filename);
+                if (!extensions.contains(suffix)) {
+                    filename.chop(suffix.length());
+                    filename += MIMETypeRegistry::getPreferredExtensionForMIMEType(mimeType);
+                }
+                response.setSuggestedFilename(filename);
+            }
+        }
 
         response.setHTTPStatusCode(statusCode);
         response.setHTTPStatusText(m_replyWrapper->reply()->attribute(QNetworkRequest::HttpReasonPhraseAttribute).toByteArray().constData());
diff --git a/Source/WebCore/platform/qt/MIMETypeRegistryQt.cpp b/Source/WebCore/platform/qt/MIMETypeRegistryQt.cpp
index 850770d1ab5..667291abdbc 100644
--- a/Source/WebCore/platform/qt/MIMETypeRegistryQt.cpp
+++ b/Source/WebCore/platform/qt/MIMETypeRegistryQt.cpp
@@ -56,6 +56,28 @@ String MIMETypeRegistry::getMIMETypeForPath(const String& path)
     return defaultMIMEType();
 }
 
+Vector<String> MIMETypeRegistry::getExtensionsForMIMEType(const String& mimeTypeName)
+{
+    Vector<String> extensions;
+    QMimeType mimeType = QMimeDatabase().mimeTypeForName(mimeTypeName);
+    if (mimeType.isValid() && !mimeType.isDefault()) {
+        Q_FOREACH(const QString& suffix, mimeType.suffixes()) {
+            extensions.append(suffix);
+        }
+    }
+
+    return extensions;
+}
+
+String MIMETypeRegistry::getPreferredExtensionForMIMEType(const String& mimeTypeName)
+{
+    QMimeType mimeType = QMimeDatabase().mimeTypeForName(mimeTypeName);
+    if (mimeType.isValid() && !mimeType.isDefault())
+        return mimeType.preferredSuffix();
+
+    return String();
+}
+
 String MIMETypeRegistry::getNormalizedMIMEType(const String& mimeTypeName)
 {
     // This looks up the mime type object by preferred name or alias, and returns the preferred name.