diff --git a/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache b/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache
index 0da998eb5060..4188010a9cc2 100644
--- a/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-qt-client/api-body.mustache
@@ -397,7 +397,7 @@ void {{classname}}::{{nickname}}({{#allParams}}{{#required}}const {{{dataType}}}
         }
         fullPath.append(paramString);
         {{/isPrimitiveType}}{{#isPrimitiveType}}
-        fullPath.append(QUrl::toPercentEncoding("{{baseName}}")).append(querySuffix).append(QUrl::toPercentEncoding(::{{cppNamespace}}::toStringValue({{paramName}}{{^required}}.value(){{/required}})));
+        fullPath.append(QUrl::toPercentEncoding("{{baseName}}")).append(querySuffix).append(QUrl::toPercentEncoding({{paramName}}{{^required}}.stringValue(){{/required}}));
 {{/isPrimitiveType}}
 {{/collectionFormat}}
 {{#collectionFormat}}
diff --git a/modules/openapi-generator/src/main/resources/cpp-qt-client/helpers-header.mustache b/modules/openapi-generator/src/main/resources/cpp-qt-client/helpers-header.mustache
index 75523b15ebff..a7bccbe67950 100644
--- a/modules/openapi-generator/src/main/resources/cpp-qt-client/helpers-header.mustache
+++ b/modules/openapi-generator/src/main/resources/cpp-qt-client/helpers-header.mustache
@@ -21,27 +21,6 @@
 namespace {{this}} {
 {{/cppNamespaceDeclarations}}
 
-template <typename T>
-class OptionalParam {
-public:
-    T m_Value;
-    bool m_hasValue;
-public:
-    OptionalParam(){
-        m_hasValue = false;
-    }
-    OptionalParam(const T &val){
-        m_hasValue = true;
-        m_Value = val;
-    }
-    bool hasValue() const {
-        return m_hasValue;
-    }
-    T value() const{
-        return m_Value;
-    }
-};
-
 bool setDateTimeFormat(const QString &format);
 bool setDateTimeFormat(const Qt::DateFormat &format);
 
@@ -264,6 +243,37 @@ bool fromJsonValue(QMap<QString, T> &val, const QJsonValue &jval) {
     return ok;
 }
 
+template <typename T>
+class OptionalParam {
+public:
+    T m_Value;
+    bool m_isNull = false;
+    bool m_hasValue;
+public:
+    OptionalParam(){
+        m_hasValue = false;
+    }
+    OptionalParam(const T &val, bool isNull = false){
+        m_hasValue = true;
+        m_Value = val;
+        m_isNull = isNull;
+    }
+    bool hasValue() const {
+        return m_hasValue;
+    }
+    T value() const{
+        return m_Value;
+    }
+
+    QString stringValue() const {
+        if (m_isNull) {
+            return QStringLiteral("");
+        } else {
+            return toStringValue(value());
+        }
+    }
+};
+
 {{#cppNamespaceDeclarations}}
 } // namespace {{this}}
 {{/cppNamespaceDeclarations}}
diff --git a/samples/client/petstore/cpp-qt/client/PFXHelpers.h b/samples/client/petstore/cpp-qt/client/PFXHelpers.h
index ad1c3bb0cdad..3503fff75236 100644
--- a/samples/client/petstore/cpp-qt/client/PFXHelpers.h
+++ b/samples/client/petstore/cpp-qt/client/PFXHelpers.h
@@ -29,27 +29,6 @@
 
 namespace test_namespace {
 
-template <typename T>
-class OptionalParam {
-public:
-    T m_Value;
-    bool m_hasValue;
-public:
-    OptionalParam(){
-        m_hasValue = false;
-    }
-    OptionalParam(const T &val){
-        m_hasValue = true;
-        m_Value = val;
-    }
-    bool hasValue() const {
-        return m_hasValue;
-    }
-    T value() const{
-        return m_Value;
-    }
-};
-
 bool setDateTimeFormat(const QString &format);
 bool setDateTimeFormat(const Qt::DateFormat &format);
 
@@ -272,6 +251,37 @@ bool fromJsonValue(QMap<QString, T> &val, const QJsonValue &jval) {
     return ok;
 }
 
+template <typename T>
+class OptionalParam {
+public:
+    T m_Value;
+    bool m_isNull = false;
+    bool m_hasValue;
+public:
+    OptionalParam(){
+        m_hasValue = false;
+    }
+    OptionalParam(const T &val, bool isNull = false){
+        m_hasValue = true;
+        m_Value = val;
+        m_isNull = isNull;
+    }
+    bool hasValue() const {
+        return m_hasValue;
+    }
+    T value() const{
+        return m_Value;
+    }
+
+    QString stringValue() const {
+        if (m_isNull) {
+            return QStringLiteral("");
+        } else {
+            return toStringValue(value());
+        }
+    }
+};
+
 } // namespace test_namespace
 
 #endif // PFX_HELPERS_H
diff --git a/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp b/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp
index 86c362b90a80..7949f0afa3a4 100644
--- a/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp
+++ b/samples/client/petstore/cpp-qt/client/PFXUserApi.cpp
@@ -655,7 +655,7 @@ void PFXUserApi::loginUser(const QString &username, const QString &password) {
         else
             fullPath.append("?");
 
-        fullPath.append(QUrl::toPercentEncoding("username")).append(querySuffix).append(QUrl::toPercentEncoding(::test_namespace::toStringValue(username)));
+        fullPath.append(QUrl::toPercentEncoding("username")).append(querySuffix).append(QUrl::toPercentEncoding(username));
     }
     
     {
@@ -670,7 +670,7 @@ void PFXUserApi::loginUser(const QString &username, const QString &password) {
         else
             fullPath.append("?");
 
-        fullPath.append(QUrl::toPercentEncoding("password")).append(querySuffix).append(QUrl::toPercentEncoding(::test_namespace::toStringValue(password)));
+        fullPath.append(QUrl::toPercentEncoding("password")).append(querySuffix).append(QUrl::toPercentEncoding(password));
     }
     PFXHttpRequestWorker *worker = new PFXHttpRequestWorker(this, _manager);
     worker->setTimeOut(_timeOut);