diff --git a/modules/hivemq/src/main/java/org/testcontainers/hivemq/HiveMQExtension.java b/modules/hivemq/src/main/java/org/testcontainers/hivemq/HiveMQExtension.java
index 91e984835d6..93d35f44d42 100644
--- a/modules/hivemq/src/main/java/org/testcontainers/hivemq/HiveMQExtension.java
+++ b/modules/hivemq/src/main/java/org/testcontainers/hivemq/HiveMQExtension.java
@@ -152,7 +152,7 @@ private void putSubclassesIntoJar(
             for (final String subClassName : subClassNames) {
                 final String className = subClassName.replaceAll("/", ".");
 
-                if (!className.startsWith("[L")) {
+                if (!className.startsWith("[")) {
                     LOGGER.debug("Trying to package subclass '{}' into extension '{}'.", className, extensionId);
                     javaArchive.addClass(className);
                 } else {
diff --git a/modules/hivemq/src/test/java/org/testcontainers/hivemq/ContainerWithExtensionSubclassIT.java b/modules/hivemq/src/test/java/org/testcontainers/hivemq/ContainerWithExtensionSubclassIT.java
index a907b8f2d2e..66dd401528a 100755
--- a/modules/hivemq/src/test/java/org/testcontainers/hivemq/ContainerWithExtensionSubclassIT.java
+++ b/modules/hivemq/src/test/java/org/testcontainers/hivemq/ContainerWithExtensionSubclassIT.java
@@ -4,6 +4,7 @@
 import org.junit.jupiter.api.Timeout;
 import org.slf4j.event.Level;
 import org.testcontainers.hivemq.util.MyExtensionWithSubclasses;
+import org.testcontainers.hivemq.util.PrimitiveArrayClass;
 import org.testcontainers.hivemq.util.TestPublishModifiedUtil;
 import org.testcontainers.utility.DockerImageName;
 import org.testcontainers.utility.MountableFile;
@@ -21,6 +22,7 @@ void test() throws Exception {
             .name("my-extension")
             .version("1.0")
             .mainClass(MyExtensionWithSubclasses.class)
+            .addAdditionalClass(PrimitiveArrayClass.class)
             .build();
 
         try (
diff --git a/modules/hivemq/src/test/java/org/testcontainers/hivemq/util/PrimitiveArrayClass.java b/modules/hivemq/src/test/java/org/testcontainers/hivemq/util/PrimitiveArrayClass.java
new file mode 100644
index 00000000000..128fe359707
--- /dev/null
+++ b/modules/hivemq/src/test/java/org/testcontainers/hivemq/util/PrimitiveArrayClass.java
@@ -0,0 +1,12 @@
+package org.testcontainers.hivemq.util;
+
+/**
+ * Helper class that generates a primitive array descriptor ("[B")
+ * in the constant pool through a byte array cast.
+ */
+public class PrimitiveArrayClass {
+
+    public void castToByteArray(Object value) {
+        byte[] ignored = (byte[]) value;
+    }
+}