diff --git a/src/librssguard/core/feeddownloader.cpp b/src/librssguard/core/feeddownloader.cpp
index 454d6f9b6..0b0830cce 100644
--- a/src/librssguard/core/feeddownloader.cpp
+++ b/src/librssguard/core/feeddownloader.cpp
@@ -123,16 +123,15 @@ void FeedDownloader::updateOneFeed(Feed* feed) {
     // Perform per-message filtering.
     QJSEngine filter_engine;
 
+    MessageFilter::initializeFilteringEngine(filter_engine);
+
     // Create JavaScript communication wrapper for the message.
     MessageObject msg_obj(&database, feed->customId(), feed->getParentServiceRoot()->accountId());
 
     // Register the wrapper.
     auto js_object = filter_engine.newQObject(&msg_obj);
 
-    filter_engine.installExtensions(QJSEngine::Extension::ConsoleExtension);
     filter_engine.globalObject().setProperty("msg", js_object);
-    filter_engine.globalObject().setProperty("MSG_ACCEPT", int(FilteringAction::Accept));
-    filter_engine.globalObject().setProperty("MSG_IGNORE", int(FilteringAction::Ignore));
 
     qDebugNN << LOGSEC_FEEDDOWNLOADER << "Setting up JS evaluation took " << tmr.nsecsElapsed() / 1000 << " microseconds.";
 
diff --git a/src/librssguard/core/messagefilter.cpp b/src/librssguard/core/messagefilter.cpp
index 602aa78f1..b4b14c50d 100755
--- a/src/librssguard/core/messagefilter.cpp
+++ b/src/librssguard/core/messagefilter.cpp
@@ -5,8 +5,6 @@
 #include "core/message.h"
 #include "exceptions/filteringexception.h"
 
-#include <QJSEngine>
-
 MessageFilter::MessageFilter(int id, QObject* parent) : QObject(parent), m_id(id) {}
 
 FilteringAction MessageFilter::filterMessage(QJSEngine* engine) {
@@ -81,6 +79,12 @@ void MessageFilter::setScript(const QString& script) {
   m_script = script;
 }
 
+void MessageFilter::initializeFilteringEngine(QJSEngine& engine) {
+  engine.installExtensions(QJSEngine::Extension::ConsoleExtension);
+  engine.globalObject().setProperty("MSG_ACCEPT", int(FilteringAction::Accept));
+  engine.globalObject().setProperty("MSG_IGNORE", int(FilteringAction::Ignore));
+}
+
 void MessageFilter::setId(int id) {
   m_id = id;
 }
diff --git a/src/librssguard/core/messagefilter.h b/src/librssguard/core/messagefilter.h
index 393161ea0..f3d9d7a4b 100755
--- a/src/librssguard/core/messagefilter.h
+++ b/src/librssguard/core/messagefilter.h
@@ -7,7 +7,7 @@
 
 #include "core/message.h"
 
-class QJSEngine;
+#include <QJSEngine>
 
 // Class which represents one message filter.
 class MessageFilter : public QObject {
@@ -27,6 +27,8 @@ class MessageFilter : public QObject {
     QString script() const;
     void setScript(const QString& script);
 
+    static void initializeFilteringEngine(QJSEngine& engine);
+
   private:
     int m_id;
     QString m_name;
diff --git a/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp b/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp
index ab27f861b..e38f63fb5 100644
--- a/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp
+++ b/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp
@@ -147,6 +147,9 @@ void FormMessageFiltersManager::loadFilter() {
 void FormMessageFiltersManager::testFilter() {
   // Perform per-message filtering.
   QJSEngine filter_engine;
+
+  MessageFilter::initializeFilteringEngine(filter_engine);
+
   QSqlDatabase database = qApp->database()->connection(metaObject()->className());
 
   // Create JavaScript communication wrapper for the message.
@@ -155,10 +158,7 @@ void FormMessageFiltersManager::testFilter() {
   // Register the wrapper.
   auto js_object = filter_engine.newQObject(&msg_obj);
 
-  filter_engine.installExtensions(QJSEngine::Extension::ConsoleExtension);
   filter_engine.globalObject().setProperty("msg", js_object);
-  filter_engine.globalObject().setProperty("MSG_ACCEPT", int(FilteringAction::Accept));
-  filter_engine.globalObject().setProperty("MSG_IGNORE", int(FilteringAction::Ignore));
 
   Message msg = testingMessage();
 
diff --git a/src/librssguard/services/gmail/network/gmailnetworkfactory.cpp b/src/librssguard/services/gmail/network/gmailnetworkfactory.cpp
index a305a0dae..72dcd69a9 100644
--- a/src/librssguard/services/gmail/network/gmailnetworkfactory.cpp
+++ b/src/librssguard/services/gmail/network/gmailnetworkfactory.cpp
@@ -97,9 +97,9 @@ QString GmailNetworkFactory::sendEmail(Mimesis::Message msg, Message* reply_to_m
   if (result.first != QNetworkReply::NetworkError::NoError) {
     if (!out.isEmpty()) {
       QJsonDocument doc = QJsonDocument::fromJson(out);
-      auto msg = doc.object()["error"].toObject()["message"].toString();
+      auto json_message = doc.object()["error"].toObject()["message"].toString();
 
-      throw ApplicationException(msg);
+      throw ApplicationException(json_message);
     }
     else {
       throw ApplicationException(QString::fromUtf8(out));
@@ -464,9 +464,9 @@ QMap<QString, QString> GmailNetworkFactory::getMessageMetadata(const QString& ms
   if (res.first == QNetworkReply::NetworkError::NoError) {
     QJsonDocument doc = QJsonDocument::fromJson(output);
     QMap<QString, QString> result;
-    auto headers = doc.object()["payload"].toObject()["headers"].toArray();
+    auto json_headers = doc.object()["payload"].toObject()["headers"].toArray();
 
-    for (const auto& header : headers) {
+    for (const auto& header : json_headers) {
       QJsonObject obj_header = header.toObject();
 
       result.insert(obj_header["name"].toString(), obj_header["value"].toString());