Nested designators error

[sanxiyn]

struct s {
  struct {
    int i;
    int j;
  } t;
  int k;
};

int main() {
  struct s x = {.t.i = 1, .k = 2};
}

gives an error:

test.c:10:   struct s x = {.t.i = 1, .k = 2};
                                   ^ expected an expression