diff --git a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Authorization.java b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Authorization.java
index 5b8e772877..b47a11d69b 100644
--- a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Authorization.java
+++ b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Authorization.java
@@ -487,7 +487,7 @@ public class Authorization {
 
     private String generateCodeVerifier(int size) {
         String verifierBytes = StringUtils.getRandomAlphanumeric(size);
-        return Base64.getUrlEncoder().withoutPadding().encodeToString(verifierBytes.getBytes());
+        return Base64.getUrlEncoder().withoutPadding().encodeToString(verifierBytes.getBytes(StandardCharsets.UTF_8));
     }
 
     public void addBasicHeaders(Request req) {
diff --git a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/RestApi.java b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/RestApi.java
index 4c3412d966..05dda9ccb8 100644
--- a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/RestApi.java
+++ b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/RestApi.java
@@ -15,6 +15,7 @@ package org.openhab.binding.mercedesme.internal.api;
 import static org.openhab.binding.mercedesme.internal.Constants.*;
 
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -149,7 +150,7 @@ public class RestApi extends Authorization {
                 for (int i = 0; i < words.length; i++) {
                     String word = words[i];
                     word = word.isEmpty() ? word
-                            : Character.toUpperCase(word.charAt(0)) + word.substring(1).toLowerCase();
+                            : Character.toUpperCase(word.charAt(0)) + word.substring(1).toLowerCase(Locale.ROOT);
                     builder.append(word);
                 }
                 String value = ((JSONObject) object).get("isAvailable").toString();
diff --git a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Websocket.java b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Websocket.java
index a4df229851..27979039ea 100644
--- a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Websocket.java
+++ b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/api/Websocket.java
@@ -16,6 +16,7 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.net.URI;
 import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -320,7 +321,7 @@ public class Websocket extends RestApi {
             try {
                 String pingId = UUID.randomUUID().toString();
                 pingPongMap.put(pingId, Instant.now());
-                localSession.getRemote().sendPing(ByteBuffer.wrap(pingId.getBytes()));
+                localSession.getRemote().sendPing(ByteBuffer.wrap(pingId.getBytes(StandardCharsets.UTF_8)));
             } catch (IOException e) {
                 logger.warn("Websocket ping failed {}", e.getMessage());
             }
@@ -333,7 +334,7 @@ public class Websocket extends RestApi {
         for (int i = 0; i < frame.getPayloadLength(); i++) {
             bytes[i] = buffer.get(i);
         }
-        String payloadString = new String(bytes);
+        String payloadString = new String(bytes, StandardCharsets.UTF_8);
         Instant sent = pingPongMap.remove(payloadString);
         if (sent == null) {
             logger.debug("Websocket received pong without ping {}", payloadString);
diff --git a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/discovery/MercedesMeDiscoveryService.java b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/discovery/MercedesMeDiscoveryService.java
index 893b4deeb0..3524e0d223 100644
--- a/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/discovery/MercedesMeDiscoveryService.java
+++ b/bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/discovery/MercedesMeDiscoveryService.java
@@ -12,6 +12,7 @@
  */
 package org.openhab.binding.mercedesme.internal.discovery;
 
+import java.util.Locale;
 import java.util.Map;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -61,7 +62,7 @@ public class MercedesMeDiscoveryService extends AbstractDiscoveryService {
             properties.put("vin", vin);
             thingDiscovered(DiscoveryResultBuilder.create(new ThingUID(ttuid, ac.getThing().getUID(), vin))
                     .withBridge(ac.getThing().getUID()).withProperties(properties).withRepresentationProperty("vin")
-                    .withLabel("Mercedes Benz " + ttuid.getId().toUpperCase()).build());
+                    .withLabel("Mercedes Benz " + ttuid.getId().toUpperCase(Locale.ROOT)).build());
         }
     }
 
diff --git a/bundles/org.openhab.binding.mercedesme/src/test/java/org/openhab/binding/mercedesme/internal/handler/ThingCallbackListener.java b/bundles/org.openhab.binding.mercedesme/src/test/java/org/openhab/binding/mercedesme/internal/handler/ThingCallbackListener.java
index f18924f9cd..8de45407a2 100644
--- a/bundles/org.openhab.binding.mercedesme/src/test/java/org/openhab/binding/mercedesme/internal/handler/ThingCallbackListener.java
+++ b/bundles/org.openhab.binding.mercedesme/src/test/java/org/openhab/binding/mercedesme/internal/handler/ThingCallbackListener.java
@@ -21,7 +21,6 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.eclipse.jdt.annotation.Nullable;
@@ -55,11 +54,15 @@ public class ThingCallbackListener implements ThingHandlerCallback {
     public Map<String, State> updatesReceived = new HashMap<>();
     public Map<String, Map<String, State>> updatesPerGroupMap = new HashMap<>();
     public boolean linked = false;
-    public Optional<ThingStatusInfo> status = Optional.empty();
+    private @Nullable ThingStatusInfo status;
     private Instant waitTime = Instant.MAX;
 
     public ThingStatusInfo getThingStatus() {
-        return status.get();
+        ThingStatusInfo localStatus = status;
+        if (localStatus == null) {
+            throw new IllegalStateException("No status update received yet");
+        }
+        return localStatus;
     }
 
     public int getUpdatesForGroup(String group) {
@@ -108,7 +111,7 @@ public class ThingCallbackListener implements ThingHandlerCallback {
 
     @Override
     public void statusUpdated(Thing thing, ThingStatusInfo thingStatus) {
-        status = Optional.of(thingStatus);
+        status = thingStatus;
     }
 
     @Override