custom netty decoder in OSGi

I have created a custom netty decoder using Camel 2.13.2 in ServiceMix
5.1.2. I would like to register the decoder as a service in ServiceMix.
All goes well, except that when I try and use the decoder in a separate
bundles blueprint, I get the error message:

14:21:21,830 | WARN | mix-5.1.2/deploy | NettyConfiguration
| 214 - org.apache.camel.camel-netty - 2.13.2 | The decoder
com.x.y.z.MyFrameD
ecoder [ at ] 1f2293f6 is not @Shareable or an ChannelHandlerFactory instance. The
decoder cannot safely be used.

I added the annotation @Sharable to the decoder and get the same error
message after redeploying. I even tried creating a class that implements
ChannelHandlerFactory and got the same message.

Is there a better approach to get this working?

Thanks,
Mark