diff --git a/src/plugins/qtsupport/baseqtversion.cpp b/src/plugins/qtsupport/baseqtversion.cpp
index 7c925433f9d..34c82067fc0 100644
--- a/src/plugins/qtsupport/baseqtversion.cpp
+++ b/src/plugins/qtsupport/baseqtversion.cpp
@@ -1215,16 +1215,16 @@ Utils::FileName BaseQtVersion::mkspecFromVersionInfo(const QHash<QString, QStrin
     // qDebug() << "default mkspec is located at" << mkspecFullPath;
 
 #ifdef Q_OS_WIN
-    QFile f2(mkspecFullPath.toString() + "/qmake.conf");
+    QFile f2(mkspecFullPath.toString() + QLatin1String("/qmake.conf"));
     if (f2.exists() && f2.open(QIODevice::ReadOnly)) {
         while (!f2.atEnd()) {
             QByteArray line = f2.readLine();
             if (line.startsWith("QMAKESPEC_ORIGINAL")) {
                 const QList<QByteArray> &temp = line.split('=');
                 if (temp.size() == 2) {
-                    QString possibleFullPath = temp.at(1).trimmed();
+                    QString possibleFullPath = QString::fromLocal8Bit(temp.at(1).trimmed().constData());
                     // We sometimes get a mix of different slash styles here...
-                    possibleFullPath = possibleFullPath.replace('\\', '/');
+                    possibleFullPath = possibleFullPath.replace(QLatin1Char('\\'), QLatin1Char('/'));
                     if (QFileInfo(possibleFullPath).exists()) // Only if the path exists
                         mkspecFullPath = Utils::FileName::fromUserInput(possibleFullPath);
                 }
@@ -1234,7 +1234,7 @@ Utils::FileName BaseQtVersion::mkspecFromVersionInfo(const QHash<QString, QStrin
         f2.close();
     }
 #elif defined(Q_OS_MAC)
-    QFile f2(mkspecFullPath.toString() + "/qmake.conf");
+    QFile f2(mkspecFullPath.toString() + QLatin1String("/qmake.conf"));
     if (f2.exists() && f2.open(QIODevice::ReadOnly)) {
         while (!f2.atEnd()) {
             QByteArray line = f2.readLine();
@@ -1245,7 +1245,7 @@ Utils::FileName BaseQtVersion::mkspecFromVersionInfo(const QHash<QString, QStrin
                     if (value.contains("XCODE")) {
                         // we don't want to generate xcode projects...
 //                      qDebug() << "default mkspec is xcode, falling back to g++";
-                        mkspecFullPath = baseMkspecDir.appendPath("macx-g++");
+                        mkspecFullPath = baseMkspecDir.appendPath(QLatin1String("macx-g++"));
                     }
                     //resolve mkspec link
                     mkspecFullPath = Utils::FileName::fromString(mkspecFullPath.toFileInfo().canonicalFilePath());
diff --git a/src/plugins/qtsupport/exampleslistmodel.cpp b/src/plugins/qtsupport/exampleslistmodel.cpp
index 5a569010e58..aab018f927e 100644
--- a/src/plugins/qtsupport/exampleslistmodel.cpp
+++ b/src/plugins/qtsupport/exampleslistmodel.cpp
@@ -136,7 +136,7 @@ QList<ExampleItem> ExamplesListModel::parseExamples(QXmlStreamReader* reader, co
         case QXmlStreamReader::EndElement:
             if (reader->name() == QLatin1String("example")) {
                 if (item.projectPath.isEmpty() || !QFileInfo(item.projectPath).exists())
-                    item.tags.append("broken");
+                    item.tags.append(QLatin1String("broken"));
                 examples.append(item);
             } else if (reader->name() == QLatin1String("examples")) {
                 return examples;
diff --git a/src/plugins/qtsupport/qtsupport.pro b/src/plugins/qtsupport/qtsupport.pro
index dd9bd0b9650..89c691211b3 100644
--- a/src/plugins/qtsupport/qtsupport.pro
+++ b/src/plugins/qtsupport/qtsupport.pro
@@ -68,5 +68,4 @@ FORMS   +=  \
     qtversionmanager.ui \
 
 
-DEFINES += QT_NO_CAST_TO_ASCII
-
+DEFINES += QT_NO_CAST_FROM_ASCII
diff --git a/src/plugins/qtsupport/qtsupport.qbs b/src/plugins/qtsupport/qtsupport.qbs
index 708b4f2d7df..ef6b50879a1 100644
--- a/src/plugins/qtsupport/qtsupport.qbs
+++ b/src/plugins/qtsupport/qtsupport.qbs
@@ -22,6 +22,7 @@ QtcPlugin {
     ]
     cpp.defines: {
         return base.concat([
+            "QT_NO_CAST_FROM_ASCII",
             "QT_NO_CAST_TO_ASCII",
             "QMAKE_AS_LIBRARY",
             "QMAKE_LIBRARY",
diff --git a/src/shared/proparser/qmakeevaluator.cpp b/src/shared/proparser/qmakeevaluator.cpp
index a81db9265bd..4b9c77d2a8f 100644
--- a/src/shared/proparser/qmakeevaluator.cpp
+++ b/src/shared/proparser/qmakeevaluator.cpp
@@ -893,15 +893,16 @@ void QMakeEvaluator::loadDefaults()
     vars[ProString("QMAKE_HOST.arch")] << archStr;
 
 # if defined(Q_CC_MSVC) // ### bogus condition, but nobody x-builds for msvc with a different qmake
-    QString paths = m_option->getEnv("PATH");
-    QString vcBin64 = m_option->getEnv("VCINSTALLDIR");
-    if (!vcBin64.endsWith('\\'))
-        vcBin64.append('\\');
-    vcBin64.append("bin\\amd64");
-    QString vcBinX86_64 = m_option->getEnv("VCINSTALLDIR");
-    if (!vcBinX86_64.endsWith('\\'))
-        vcBinX86_64.append('\\');
-    vcBinX86_64.append("bin\\x86_amd64");
+    QLatin1Char backslash('\\');
+    QString paths = m_option->getEnv(QLatin1String("PATH"));
+    QString vcBin64 = m_option->getEnv(QLatin1String("VCINSTALLDIR"));
+    if (!vcBin64.endsWith(backslash))
+        vcBin64.append(backslash);
+    vcBin64.append(QLatin1String("bin\\amd64"));
+    QString vcBinX86_64 = m_option->getEnv(QLatin1String("VCINSTALLDIR"));
+    if (!vcBinX86_64.endsWith(backslash))
+        vcBinX86_64.append(backslash);
+    vcBinX86_64.append(QLatin1String("bin\\x86_amd64"));
     if (paths.contains(vcBin64, Qt::CaseInsensitive)
             || paths.contains(vcBinX86_64, Qt::CaseInsensitive))
         vars[ProString("QMAKE_TARGET.arch")] << ProString("x86_64", NoHash);