Avahi with the mono keyword fails to compile with the stable mono ebuild. The Mono.Unix namespace is required and was added in 1.1.3. Reproducible: Always Steps to Reproduce: 1. 'USE="mono" emerge avahi' with mono 1.0.5-r5 installed 2. 3. Fixed problem by adding "dev-lang/mono ~x86" to package.keywords and emerging mono Line 24 of the avahi 0.5 ebuild should be " mono? ( >=dev-lang/mono-1.1.3 )"
Fixed in CVS. Thanks Frederick!