Cannot enable proxy_arp for WiFi

I'm trying to enable proxy_arp=1 for WiFi. The configuration is created correctly, but hostapd doesn't know about the option:

Fri Mar  8 21:42:25 2024 daemon.err hostapd: Line 52: unknown configuration item 'proxy_arp'

I tried the packages wpad-mbedtls and hostapd-mbedtls since those are the full-featured builds - or am I wrong here?