diff --git a/src/main/java/com/rabbitmq/client/amqp/impl/AmqpMessage.java b/src/main/java/com/rabbitmq/client/amqp/impl/AmqpMessage.java
index 5dcdad6e3..988f7cab9 100644
--- a/src/main/java/com/rabbitmq/client/amqp/impl/AmqpMessage.java
+++ b/src/main/java/com/rabbitmq/client/amqp/impl/AmqpMessage.java
@@ -499,6 +499,7 @@ public Object annotation(String key) {
 
   @Override
   public Message annotation(String key, Object value) {
+    Utils.validateMessageAnnotationKey(key);
     callOnDelegate(m -> m.annotation(key, value));
     return this;
   }
diff --git a/src/main/java/com/rabbitmq/client/amqp/impl/Utils.java b/src/main/java/com/rabbitmq/client/amqp/impl/Utils.java
index b846992a0..e2689baac 100644
--- a/src/main/java/com/rabbitmq/client/amqp/impl/Utils.java
+++ b/src/main/java/com/rabbitmq/client/amqp/impl/Utils.java
@@ -100,13 +100,13 @@ private static boolean isJava21OrMore() {
   }
 
   static void checkMessageAnnotations(Map<String, Object> annotations) {
-    annotations.forEach(
-        (k, v) -> {
-          if (!k.startsWith("x-")) {
-            throw new IllegalArgumentException(
-                "Message annotation keys must start with 'x-': " + k);
-          }
-        });
+    annotations.forEach((k, v) -> validateMessageAnnotationKey(k));
+  }
+
+  static void validateMessageAnnotationKey(String key) {
+    if (!key.startsWith("x-")) {
+      throw new IllegalArgumentException("Message annotation keys must start with 'x-': " + key);
+    }
   }
 
   private static class NamedThreadFactory implements ThreadFactory {