Apple Mach-O Linker(Id) Error when building Unity project

I am trying to build a Unity AR project onto my iPhone SE. However, I am getting the following error. Undefined symbols for architecture arm64: "void RegisterClass(char const*)", referenced from: RegisterAllClasses() in UnityClassRegistration.o ld: symbol(s) not found for architecture arm64 clang: error: linker command failed with exit code 1 (use -v to see invocation) I checked and found there is a cpp file UnityClassRegistration under the Native folder. It has a line `class WorldAnchor; template <> void RegisterClass(const char*); ` I am on Unity 2018.1.1 . Removing the class WorldAnchor lets me get past this error. But I want to know why this error is appearing in the first place. Do I need to add something to the Unity scene to get past this error? My Xcode version is 9.4 .