build-sys: use ${ac_default_prefix}

diff --git a/configure.ac b/configure.ac
index 636b69e677eb0c6325022debd93c50a8672cb0d5..4c8b1156743f733a7eaf87ee547093e1ed34cc51 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -599,7 +599,7 @@ AC_ARG_WITH([udevrulesdir],
 
 AC_ARG_WITH([rootprefix],
         AS_HELP_STRING([--with-rootprefix=DIR], [rootfs directory prefix for config files and kernel modules]),
-        [], [with_rootprefix=${prefix}])
+        [], [with_rootprefix=${ac_default_prefix}])
 
 AC_ARG_WITH([rootlibdir],
         AS_HELP_STRING([--with-rootlibdir=DIR], [Root directory for libraries necessary for boot]),