ClassCastException for instance-identifier in leafref

grouping someGrouping {
container someContainer {
leaf someLeaf

{ type instance-identifier; }

}
}

rpc make-foo {
input {
leaf qs {
type leafref

{ path "../../../someGrouping/someContainer/someLeaf"; }

}
}
output {
leaf result

{ type string; }

}
}

I invoke RPC with this input:
<input>
<qs xmlns:np="namespaceOfSomeModule">/np:foo/np:bar[np:name="someValue"]</qs>
</input>

ERROR o.o.c.sal.restconf.impl.RestCodec - ClassCastException was thrown when codec is invoked with parameter
java.lang.ClassCastException: org.opendaylight.controller.sal.restconf.impl.IdentityValuesDTO cannot be cast to java.lang.String
at org.opendaylight.controller.sal.restconf.impl.RestCodec$LeafrefCodecImpl.deserialize(RestCodec.java:183) ~[bundlefile:na]
at org.opendaylight.controller.sal.restconf.impl.RestCodec$ObjectCodec.deserialize(RestCodec.java:92) ~[bundlefile:na]
at org.opendaylight.controller.sal.restconf.impl.RestconfImpl.normalizeNode(RestconfImpl.java:1353) [bundlefile:na]
at org.opendaylight.controller.sal.restconf.impl.RestconfImpl.normalizeNode(RestconfImpl.java:1289) [bundlefile:na]
at org.opendaylight.controller.sal.restconf.impl.RestconfImpl.normalizeNode(RestconfImpl.java:1196) [bundlefile:na]
at org.opendaylight.controller.sal.restconf.impl.RestconfImpl.callRpc(RestconfImpl.java:613) [bundlefile:na]
at org.opendaylight.controller.sal.restconf.impl.RestconfImpl.invokeRpc(RestconfImpl.java:566) [bundlefile:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_51]