This error dates back to Unity Pro v8.0. It was corrected in V8.0 using patches and no longer exists in current versions. If you are seeing it in a current version of Unity, it is likely that your project is running the V8.0 libset. If you export your project to ZEF/XEF and then open the file and build all, this will update the libset to the version of Unity that was used to export / import. Because this process forces us to build all offline, the processor will need to be stopped in order to transfer this new program to it.