diff --git a/plc4j/drivers/opcua/src/main/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactory.java b/plc4j/drivers/opcua/src/main/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactory.java
index a86f514956f..5b2146796cb 100644
--- a/plc4j/drivers/opcua/src/main/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactory.java
+++ b/plc4j/drivers/opcua/src/main/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactory.java
@@ -30,7 +30,8 @@
 
 public class ChunkFactory {
 
-    public static int SYMMETRIC_SECURITY_HEADER_SIZE = 4;
+    public static final int ASYMMETRIC_SECURITY_HEADER_SIZE = 59;
+    public static final int SYMMETRIC_SECURITY_HEADER_SIZE = 4;
 
     public Chunk create(boolean asymmetric, Conversation conversation) {
         return create(asymmetric,
@@ -48,7 +49,7 @@ public Chunk create(boolean asymmetric, boolean encrypted, boolean signed, Secur
 
         if (securityPolicy == SecurityPolicy.NONE) {
             return new Chunk(
-                asymmetric ? 59 : SYMMETRIC_SECURITY_HEADER_SIZE,
+                asymmetric ? ASYMMETRIC_SECURITY_HEADER_SIZE : SYMMETRIC_SECURITY_HEADER_SIZE,
                 1,
                 1,
                 securityPolicy.getSymmetricSignatureSize(),
diff --git a/plc4j/drivers/opcua/src/test/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactoryTest.java b/plc4j/drivers/opcua/src/test/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactoryTest.java
index b97632b1a1d..5f69f299879 100644
--- a/plc4j/drivers/opcua/src/test/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactoryTest.java
+++ b/plc4j/drivers/opcua/src/test/java/org/apache/plc4x/java/opcua/protocol/chunk/ChunkFactoryTest.java
@@ -26,6 +26,7 @@
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.concurrent.ConcurrentHashMap;
 import org.apache.plc4x.java.opcua.TestCertificateGenerator;
 import org.apache.plc4x.java.opcua.readwrite.MessageSecurityMode;
 import org.apache.plc4x.java.opcua.readwrite.OpcuaProtocolLimits;
@@ -38,7 +39,7 @@
 @DisableOnJenkinsFlag
 class ChunkFactoryTest {
 
-    public static final Map<Integer, Entry<PrivateKey, X509Certificate>> CERTIFICATES = new HashMap<>();
+    public static final Map<Integer, Entry<PrivateKey, X509Certificate>> CERTIFICATES = new ConcurrentHashMap<>();
 
     private OpcuaProtocolLimits limits = new OpcuaProtocolLimits(
         8196,