diff --git a/Makefile.autosetup b/Makefile.autosetup
index fb6b83dfa5e..55552db55a0 100644
--- a/Makefile.autosetup
+++ b/Makefile.autosetup
@@ -38,7 +38,6 @@ LIBBINFILES+=	$(SRCDIR)/contrib/smime_keys
 @endif
 
 # paths
-prefix=		@prefix@
 bindir=		@BINDIR@
 datadir=	@PKGDATADIR@
 docdir=		@PKGDOCDIR@
diff --git a/auto.def b/auto.def
index d922490d7dc..c871159e47e 100644
--- a/auto.def
+++ b/auto.def
@@ -85,6 +85,8 @@ options {
   with-qdbm:path            => "Location of QDBM"
   tokyocabinet=0            => "Use TokyoCabinet for the header cache"
   with-tokyocabinet:path    => "Location of TokyoCabinet"
+# System
+  with-sysroot:path         => "Target system root"
 # Enable all options
   everything=0              => "Enable all options"
 }
@@ -294,7 +296,7 @@ define USE_SOCKET
 define SUN_ATTACHMENT
 ###############################################################################
 
-set prefix [get-define prefix]
+set prefix [opt-val with-sysroot][get-define prefix]
 
 ###############################################################################
 # Everything