--- a/net-dns/bind-tools/bind-tools-9.16.4.ebuild	
+++ a/net-dns/bind-tools/bind-tools-9.16.4.ebuild	
@@ -36,9 +36,7 @@ DEPEND="${COMMON_DEPEND}"
 
 RDEPEND="${COMMON_DEPEND}"
 
-# sphinx required for man-page and html creation
 BDEPEND="${PYTHON_DEPS}
-	dev-python/sphinx
 	virtual/pkgconfig"
 
 S="${WORKDIR}/${MY_P}"
@@ -58,6 +56,9 @@ src_prepare() {
 	rm aclocal.m4 || die
 	rm -rf libtool.m4/ || die
 
+	# ensure prebuilt has a higher timestamp than source
+	touch /doc/man/*.?in
+
 	eautoreconf
 }