Exception when serializing netconf xml message that contains namespace prefix e.g. "xmlp"

2014-08-20 16:58:52.022 CEST [nettyThreadgroupModule$NioEventLoopGroupCloseable-5-10] WARN i.n.util.concurrent.DefaultPromise - An exception was thrown by org.opendaylight.controller.sal.connect.netconf.listener.NetconfDeviceCommunicator$1.operationComplete()
java.lang.IllegalStateException: Unable to serialize xml element [rpc: null]
at org.opendaylight.controller.netconf.util.xml.XmlUtil.toString(XmlUtil.java:168) ~[na:na]
at org.opendaylight.controller.netconf.util.xml.XmlUtil.toString(XmlUtil.java:149) ~[na:na]
at org.opendaylight.controller.netconf.util.xml.XmlUtil.toString(XmlUtil.java:145) ~[na:na]
at org.opendaylight.controller.sal.connect.netconf.listener.NetconfDeviceCommunicator$1.operationComplete(NetconfDeviceCommunicator.java:291) ~[na:na]
at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:679) [bundlefile:4.0.19.Final]
at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:569) [bundlefile:4.0.19.Final]
at io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:430) [bundlefile:4.0.19.Final]
at io.netty.channel.DefaultChannelHandlerContext.notifyOutboundHandlerException(DefaultChannelHandlerContext.java:759) [bundlefile:4.0.19.Final]
at io.netty.channel.DefaultChannelHandlerContext.invokeWrite(DefaultChannelHandlerContext.java:668) [bundlefile:4.0.19.Final]
at io.netty.channel.DefaultChannelHandlerContext.access$2000(DefaultChannelHandlerContext.java:30) [bundlefile:4.0.19.Final]
at io.netty.channel.DefaultChannelHandlerContext$AbstractWriteTask.write(DefaultChannelHandlerContext.java:945) [bundlefile:4.0.19.Final]
at io.netty.channel.DefaultChannelHandlerContext$WriteAndFlushTask.write(DefaultChannelHandlerContext.java:999) [bundlefile:4.0.19.Final]
at io.netty.channel.DefaultChannelHandlerContext$AbstractWriteTask.run(DefaultChannelHandlerContext.java:934) [bundlefile:4.0.19.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:370) [bundlefile:4.0.19.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:353) [bundlefile:4.0.19.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [bundlefile:4.0.19.Final]
at java.lang.Thread.run(Thread.java:745) [na:1.7.0_65]
Caused by: javax.xml.transform.TransformerException: java.lang.RuntimeException: Namespace for prefix 'xmlp' has not been declared.
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:755) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:359) ~[na:1.7.0_65]
at org.opendaylight.controller.netconf.util.xml.XmlUtil.toString(XmlUtil.java:164) ~[na:na]
... 16 common frames omitted
Caused by: java.lang.RuntimeException: Namespace for prefix 'xmlp' has not been declared.
at com.sun.org.apache.xml.internal.serializer.SerializerBase.getNamespaceURI(SerializerBase.java:914) ~[na:1.7.0_65]
at com.sun.org.apache.xml.internal.serializer.SerializerBase.addAttribute(SerializerBase.java:431) ~[na:1.7.0_65]
at com.sun.org.apache.xml.internal.serializer.ToUnknownStream.addAttribute(ToUnknownStream.java:316) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:198) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:230) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:230) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:94) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(TransformerImpl.java:702) ~[na:1.7.0_65]
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:746) ~[na:1.7.0_65]
... 18 common frames omitted