The change, which the upper house must approve, applies only to out-of-wedlock children of Japanese fathers and non-Japanese mothers. Under the new law children will be able to claim citizenship for up to 20 years after they’re born; current legislation requires a Japanese father to acknowledge the child while it’s in the womb.

As many as 20,000 children living in Japan may be eligible for citizenship after the change, said Yasuhiro Okuda, a law professor at Chuo University in Tokyo who has followed the case. Still, the legislation enforces the notion that heredity and not birthplace determines Japanese citizenship, he said.