diff -Nur linux-3.15.2.orig/usr/Kconfig linux-3.15.2/usr/Kconfig
--- linux-3.15.2.orig/usr/Kconfig	2014-06-26 21:17:52.000000000 +0200
+++ linux-3.15.2/usr/Kconfig	2014-06-30 08:29:00.000000000 +0200
@@ -174,4 +174,12 @@
 	  size is about 10% bigger than gzip; however its speed
 	  (both compression and decompression) is the fastest.
 
+config INITRAMFS_COMPRESSION_LZ4
+	bool "LZ4"
+	depends on RD_LZ4
+	help
+	  Its compression ratio is the poorest among the choices. The kernel
+	  size is about 10% bigger than gzip; however its speed
+	  (both compression and decompression) is the fastest.
+
 endchoice