--- a/net-libs/gtk-vnc/gtk-vnc-1.0.0.ebuild	
+++ a/net-libs/gtk-vnc/gtk-vnc-1.0.0.ebuild	
@@ -60,8 +60,14 @@ src_configure() {
 		$(meson_feature pulseaudio)
 		$(meson_feature sasl)
 		-Denable-werror=false
-		-Dwith-coroutine=auto # gthread on windows, libc ucontext elsewhere; neither has extra deps
 		$(meson_use vala with-vala)
 	)
+
+	if use elibc_musl; then
+		emesonargs+=-Dwith-coroutine=gthread
+	else
+		emesonargs+=-Dwith-coroutine=auto
+	fi
+
 	meson_src_configure
 }