diff --git a/src/libs/utils/fileutils.h b/src/libs/utils/fileutils.h
index 492c0b636b6..29067714ee3 100644
--- a/src/libs/utils/fileutils.h
+++ b/src/libs/utils/fileutils.h
@@ -97,7 +97,6 @@ public:
 
     using QString::clear;
     using QString::isEmpty;
-    using QString::isNull;
 
 private:
     FileName(const QString &string);
diff --git a/src/plugins/nim/project/nimtoolchain.cpp b/src/plugins/nim/project/nimtoolchain.cpp
index 22bc760aaec..80e54567be2 100644
--- a/src/plugins/nim/project/nimtoolchain.cpp
+++ b/src/plugins/nim/project/nimtoolchain.cpp
@@ -71,7 +71,7 @@ Abi NimToolChain::targetAbi() const
 
 bool NimToolChain::isValid() const
 {
-    if (m_compilerCommand.isNull())
+    if (m_compilerCommand.isEmpty())
         return false;
     QFileInfo fi = compilerCommand().toFileInfo();
     return fi.isExecutable();
diff --git a/src/plugins/projectexplorer/gcctoolchain.cpp b/src/plugins/projectexplorer/gcctoolchain.cpp
index d69d8602056..b126bc1b1ea 100644
--- a/src/plugins/projectexplorer/gcctoolchain.cpp
+++ b/src/plugins/projectexplorer/gcctoolchain.cpp
@@ -329,7 +329,7 @@ QList<Abi> GccToolChain::supportedAbis() const
 
 bool GccToolChain::isValid() const
 {
-    if (m_compilerCommand.isNull())
+    if (m_compilerCommand.isEmpty())
         return false;
 
     QFileInfo fi = compilerCommand().toFileInfo();
diff --git a/src/plugins/qbsprojectmanager/qbsbuildstep.cpp b/src/plugins/qbsprojectmanager/qbsbuildstep.cpp
index 1cd0b4f85fe..7da92d837d4 100644
--- a/src/plugins/qbsprojectmanager/qbsbuildstep.cpp
+++ b/src/plugins/qbsprojectmanager/qbsbuildstep.cpp
@@ -259,15 +259,15 @@ bool QbsBuildStep::hasCustomInstallRoot() const
 
 Utils::FileName QbsBuildStep::installRoot(VariableHandling variableHandling) const
 {
-    Utils::FileName root = Utils::FileName::fromString(qbsConfiguration(variableHandling)
-            .value(Constants::QBS_INSTALL_ROOT_KEY).toString());
-    if (root.isNull()) {
-        const QbsBuildConfiguration * const bc
-                = static_cast<QbsBuildConfiguration *>(buildConfiguration());
-        root = bc->buildDirectory().appendPath(bc->configurationName())
-                .appendPath(qbs::InstallOptions::defaultInstallRoot());
-    }
-    return root;
+    const QString root =
+            qbsConfiguration(variableHandling).value(Constants::QBS_INSTALL_ROOT_KEY).toString();
+    if (!root.isNull())
+        return Utils::FileName::fromString(root);
+
+    const QbsBuildConfiguration * const bc
+            = static_cast<QbsBuildConfiguration *>(buildConfiguration());
+    return bc->buildDirectory().appendPath(bc->configurationName())
+            .appendPath(qbs::InstallOptions::defaultInstallRoot());
 }
 
 int QbsBuildStep::maxJobs() const
diff --git a/src/plugins/qtsupport/qtoptionspage.cpp b/src/plugins/qtsupport/qtoptionspage.cpp
index c4faa5bf289..798a4713752 100644
--- a/src/plugins/qtsupport/qtoptionspage.cpp
+++ b/src/plugins/qtsupport/qtoptionspage.cpp
@@ -549,7 +549,7 @@ void QtOptionsPageWidget::addQtDir()
                                              BuildableHelperLibrary::filterForQmakeFileDialog(),
                                              0,
                                              QFileDialog::DontResolveSymlinks));
-    if (qtVersion.isNull())
+    if (qtVersion.isEmpty())
         return;
 
     QFileInfo fi = qtVersion.toFileInfo();
@@ -621,7 +621,7 @@ void QtOptionsPageWidget::editPath()
                                              BuildableHelperLibrary::filterForQmakeFileDialog(),
                                              0,
                                              QFileDialog::DontResolveSymlinks));
-    if (qtVersion.isNull())
+    if (qtVersion.isEmpty())
         return;
     BaseQtVersion *version = QtVersionFactory::createQtVersionFromQMakePath(qtVersion);
     if (!version)