--- a/app-arch/lz4/lz4-1.8.0.ebuild	    2018-01-05 20:39:17.000000000 +0100
+++ b/app-arch/lz4/lz4-1.8.0-r1.ebuild	2018-01-09 17:48:32.849978400 +0100
@@ -24,10 +24,18 @@
 # however, it is extremely unlikely that this 'const' would actually
 # be relied on
 SLOT="0/r131"
-IUSE="static-libs"
+IUSE="static-libs xxhash"
 
 CMAKE_USE_DIR=${S}/contrib/cmake_unofficial
 
+src_prepare() {
+	if use xxhash; then
+		sed -e 's|"${LZ4_LIB_SOURCE_DIR}/lz4hc.h"|"${LZ4_LIB_SOURCE_DIR}/lz4hc.h"\n    "${LZ4_LIB_SOURCE_DIR}/xxhash.h"|g' \
+			-i ${CMAKE_USE_DIR}/CMakeLists.txt
+	fi
+	eapply_user
+}
+
 multilib_src_configure() {
 	local mycmakeargs=(
 		-DBUILD_STATIC_LIBS=$(usex static-libs)