diff --git a/README b/README
index 8f2a7914..991164e5 100644
--- a/README
+++ b/README
@@ -63,7 +63,9 @@ For building on Unix:
 All of the Makefiles are generated automatically from the file
 `Recipe' by the Perl script `mkfiles.pl'. Additions and corrections
 to Recipe and the mkfiles.pl are much more useful than additions and
-corrections to the alternative Makefiles themselves.
+corrections to the alternative Makefiles themselves. The Unix `configure'
+script and its various requirements are generated by the shell script
+`mkauto.sh', which requires GNU Autoconf, GNU Automake, and Gtk.
 
 Documentation (in various formats including Windows Help and Unix
 `man' pages) is to be built from the Halibut (`.but') files in the
diff --git a/mkauto.sh b/mkauto.sh
new file mode 100755
index 00000000..cdee6221
--- /dev/null
+++ b/mkauto.sh
@@ -0,0 +1,8 @@
+#! /bin/sh
+# This script makes the autoconf mechanism for the Unix port work.
+# It's separate from mkfiles.pl because it won't work (and isn't needed)
+# on a non-Unix system.
+
+# Track down automake's copy of install-sh
+cp `aclocal --print-ac-dir | sed 's/aclocal$/automake/'`/install-sh unix/.
+(cd unix && autoreconf  && rm -rf aclocal.m4 autom4te.cache)
diff --git a/mkunxarc.sh b/mkunxarc.sh
index 8433c383..57ada304 100755
--- a/mkunxarc.sh
+++ b/mkunxarc.sh
@@ -28,9 +28,7 @@ esac
 
 perl mkfiles.pl
 (cd doc && make -s ${docver:+"$docver"})
-# Track down automake's copy of install-sh
-cp `aclocal --print-ac-dir | sed 's/aclocal$/automake/'`/install-sh unix/.
-(cd unix && autoreconf  && rm -rf aclocal.m4 autom4te.cache)
+sh mkauto.sh
 
 relver=`cat LATEST.VER`
 arcname="putty$arcsuffix"