diff --git a/src/ATBAPP/ATBDeviceControllerPlugin.cpp b/src/ATBAPP/ATBDeviceControllerPlugin.cpp
index 66eb68c..218a76e 100644
--- a/src/ATBAPP/ATBDeviceControllerPlugin.cpp
+++ b/src/ATBAPP/ATBDeviceControllerPlugin.cpp
@@ -103,7 +103,7 @@ PLUGIN_STATE ATBDeviceControllerPlugin::initDCPlugin(QObject *eventReceiver, con
     hw->vend_failed();
 
     // read sw-version and store it in persistentData, if changed
-    QString dc_fw_version = hw->dc_getSWversion();
+    QString dc_fw_version = hw->dc_getSWversion().remove(QChar('\0'));
     qCritical() << "ATBDeviceControllerPlugin: DC firmware version: " << dc_fw_version;
     this->persistentData->setDCFirmwareVersion(dc_fw_version);
     this->persistentData->serializeToFile();
diff --git a/src/ATBAPP/DeviceControllerDiag.cpp b/src/ATBAPP/DeviceControllerDiag.cpp
index c94f691..2a5f89f 100644
--- a/src/ATBAPP/DeviceControllerDiag.cpp
+++ b/src/ATBAPP/DeviceControllerDiag.cpp
@@ -45,7 +45,11 @@ void DeviceControllerDiag::diagRequest()
     this->private_startDiag();
 
     // read dc-fw-version:
-    QString dc_fw_version = hw->dc_getSWversion();
+    /* note: dc_getSWVersion() returns always 32 characters (QString)...
+     * if no version string could be read it will contain 32 null-characters:
+     * "\u0000\u0000..."
+     */
+    QString dc_fw_version = hw->dc_getSWversion().remove(QChar('\0'));
     qCritical() << "ATBDeviceControllerPlugin: DC firmware version: " << dc_fw_version;
     this->pData->setDCFirmwareVersion(dc_fw_version);
     this->pData->serializeToFile();
diff --git a/src/ATBAPP/support/PersistentData.cpp b/src/ATBAPP/support/PersistentData.cpp
index 05f2a67..cfcf305 100644
--- a/src/ATBAPP/support/PersistentData.cpp
+++ b/src/ATBAPP/support/PersistentData.cpp
@@ -125,6 +125,9 @@ QList<QString> PersistentData::uniqueKeys() const {
 
 void PersistentData::setDCFirmwareVersion(const QString & fw_version)
 {
+    // there must be a version string!
+    if (fw_version.size() < 1) return;
+
     if (this->hash["dc_fw_version"].toString() != fw_version) {
         this->isChangedFlag = true;
         this->hash.insert("dc_fw_version", fw_version);