strange thing: assign changes an arguments

I am sligtly changed example with file (added multiple phones):

message Person {
  required string name = 1;
  required int32 id = 2;
  optional string email = 3;

  repeated PhoneNumber phone = 4;
}

enum PhoneType {
    MOBILE = 0;
    HOME = 0;
    WORK = 2;
}

message PhoneNumber { 
    required string number = 1;
    optional PhoneType type = 2 [default = MOBILE];
}

import std.stdio;
import dproto.dproto;

mixin ProtocolBuffer!"person.proto";

int main()
{
    PhoneNumber phone;
    phone.number = "45345";

    Person person;
    person.name = "John Doe";
    person.id = 1234;
    person.email = "jdoe@example.com";
    person.phone ~= phone; // look here!
    person.phone ~= phone; // look here!

    ubyte[] serializedObject = person.serialize();

    Person person2 = Person(serializedObject);
    writeln("Name: ", person2.name);
    writeln("E-mail: ", person2.email);
    writeln("Phones: ", phone); // but now it contains two different values
    return 0;
}

$ dub
Target dproto 1.2.3 is up to date. Use --force to rebuild.
Building dproto_simple_file ~master configuration "application", build type debug.
Compiling using dmd...
Linking...
Running ./dproto_simple_file 
Name: John Doe
E-mail: jdoe@example.com
Phones: PhoneNumber("45345", 0) # <====== here

msoucy / dproto

strange thing: assign changes an arguments #46