ambiguous overload for 'push_back' and 'operator+='

g++ -o build/jsontest.o -c -g -rdynamic -Wall -Werror -std=c++11 -Ibuild build/jsontest.cpp
build/jsontest.cpp: In function 'int main(int, char**)':
build/jsontest.cpp:8:38: error: call of overloaded 'push_back(<brace-enclosed initializer list>)' is ambiguous
     data.push_back({"key2", "value2"});
                                      ^
build/jsontest.cpp:8:38: note: candidates are:
In file included from build/jsontest.cpp:2:0:
build/json.hpp:4668:10: note: void nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::push_back(nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>&&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator]
     void push_back(basic_json&& val)
          ^
build/json.hpp:4704:10: note: void nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::push_back(const nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator]
     void push_back(const basic_json& val)
          ^
build/json.hpp:4754:10: note: void nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::push_back(const typename nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::object_t::value_type&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; typename nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::object_t::value_type = std::pair<const std::basic_string<char>, nlohmann::basic_json<> >]
     void push_back(const typename object_t::value_type& val)
          ^
build/jsontest.cpp:9:10: error: ambiguous overload for 'operator+=' (operand types are 'json {aka nlohmann::basic_json<>}' and '<brace-enclosed initializer list>')
     data += {"key3", "value3"};
          ^
build/jsontest.cpp:9:10: note: candidates are:
In file included from build/jsontest.cpp:2:0:
build/json.hpp:4694:15: note: nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type& nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::operator+=(nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>&&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::reference = nlohmann::basic_json<>&; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type = nlohmann::basic_json<>]
     reference operator+=(basic_json&& val)
               ^
build/json.hpp:4728:15: note: nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type& nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::operator+=(const nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::reference = nlohmann::basic_json<>&; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type = nlohmann::basic_json<>]
     reference operator+=(const basic_json& val)
               ^
build/json.hpp:4778:15: note: nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type& nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::operator+=(const typename nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::object_t::value_type&) [with ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::reference = nlohmann::basic_json<>&; nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::value_type = nlohmann::basic_json<>; typename nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType>::object_t::value_type = std::pair<const std::basic_string<char>, nlohmann::basic_json<> >]
     reference operator+=(const typename object_t::value_type& val)