diff --git a/src/plugins/debugger/lldb/lldbengine.cpp b/src/plugins/debugger/lldb/lldbengine.cpp
index c9681e3e27f..deb42544a87 100644
--- a/src/plugins/debugger/lldb/lldbengine.cpp
+++ b/src/plugins/debugger/lldb/lldbengine.cpp
@@ -179,8 +179,8 @@ void LldbEngine::setupEngine()
 
     showMessage("STARTING LLDB: " + lldbCmd.toUserOutput());
     Environment environment = runParameters().debugger.environment;
-    environment.appendOrSet("QT_CREATOR_LLDB_PROCESS", "1");
-    environment.appendOrSet("PYTHONUNBUFFERED", "1");  // avoid flushing problem on macOS
+    environment.set("QT_CREATOR_LLDB_PROCESS", "1");
+    environment.set("PYTHONUNBUFFERED", "1"); // avoid flushing problem on macOS
     DebuggerItem::addAndroidLldbPythonEnv(lldbCmd, environment);
 
     if (lldbCmd.osType() == OsTypeLinux) {
diff --git a/src/plugins/qmldesigner/components/componentcore/modelnodeoperations.cpp b/src/plugins/qmldesigner/components/componentcore/modelnodeoperations.cpp
index dd00cd48d45..24fff841b6d 100644
--- a/src/plugins/qmldesigner/components/componentcore/modelnodeoperations.cpp
+++ b/src/plugins/qmldesigner/components/componentcore/modelnodeoperations.cpp
@@ -1679,7 +1679,7 @@ void openOldEffectMaker(const QString &filePath)
         arguments << "--exportpath" << effectResPath.toString();
 
         if (env.osType() == Utils::OsTypeMac)
-            env.appendOrSet("QSG_RHI_BACKEND", "metal");
+            env.set("QSG_RHI_BACKEND", "metal");
 
         Utils::Process *qqemProcess = new Utils::Process();
         qqemProcess->setEnvironment(env);
diff --git a/src/plugins/qmldesigner/puppetenvironmentbuilder.cpp b/src/plugins/qmldesigner/puppetenvironmentbuilder.cpp
index d19b1d202c6..6e8a2b60245 100644
--- a/src/plugins/qmldesigner/puppetenvironmentbuilder.cpp
+++ b/src/plugins/qmldesigner/puppetenvironmentbuilder.cpp
@@ -149,7 +149,7 @@ void PuppetEnvironmentBuilder::addControls() const
     const QString styleConfigFileName = getStyleConfigFileName();
 
     if (!styleConfigFileName.isEmpty())
-        m_environment.appendOrSet("QT_QUICK_CONTROLS_CONF", styleConfigFileName);
+        m_environment.set("QT_QUICK_CONTROLS_CONF", styleConfigFileName);
 }
 
 void PuppetEnvironmentBuilder::addPixelRatio() const
@@ -238,8 +238,7 @@ void PuppetEnvironmentBuilder::addCustomFileSelectors() const
     customFileSelectors.append("DesignMode");
 
     if (!customFileSelectors.isEmpty())
-        m_environment.appendOrSet("QML_FILE_SELECTORS",
-                                  customFileSelectors.join(","));
+        m_environment.set("QML_FILE_SELECTORS", customFileSelectors.join(","));
 
     qCInfo(puppetEnvirmentBuild) << "Puppet selectors:" << customFileSelectors;
 }
diff --git a/src/plugins/squish/squishtools.cpp b/src/plugins/squish/squishtools.cpp
index 9c3b074189c..3ed7b7efe7e 100644
--- a/src/plugins/squish/squishtools.cpp
+++ b/src/plugins/squish/squishtools.cpp
@@ -704,8 +704,8 @@ Environment SquishTools::squishEnvironment()
 {
     Environment environment = Environment::systemEnvironment();
     if (!toolsSettings.licenseKeyPath.isEmpty())
-        environment.prependOrSet("SQUISH_LICENSEKEY_DIR", toolsSettings.licenseKeyPath.nativePath());
-    environment.prependOrSet("SQUISH_PREFIX", toolsSettings.squishPath.nativePath());
+        environment.set("SQUISH_LICENSEKEY_DIR", toolsSettings.licenseKeyPath.nativePath());
+    environment.set("SQUISH_PREFIX", toolsSettings.squishPath.nativePath());
     return environment;
 }
 
diff --git a/tests/auto/utils/commandline/tst_commandline.cpp b/tests/auto/utils/commandline/tst_commandline.cpp
index fff0879148a..1c7b7d4f807 100644
--- a/tests/auto/utils/commandline/tst_commandline.cpp
+++ b/tests/auto/utils/commandline/tst_commandline.cpp
@@ -47,7 +47,7 @@ private slots:
                                   + QLatin1String(TEST_RELATIVE_LIBEXEC_PATH));
         LauncherInterface::setPathToLauncher(libExecPath);
 
-        testEnv.appendOrSet("TEST_ECHO", "1");
+        testEnv.set("TEST_ECHO", "1");
 
         if (HostOsInfo::isWindowsHost())
             newLine = "\r\n";