+dnl Check for Guile-lzlib.
+GUILE_MODULE_AVAILABLE([have_guile_lzlib], [(lzlib)])
+if test "x$have_guile_lzlib" != "xyes"; then
+ AC_MSG_ERROR([Guile-lzlib is missing; please install it.])
+fi
+
+dnl Guile-newt is used by the graphical installer.
+GUILE_MODULE_AVAILABLE([have_guile_newt], [(newt)])
+
+AC_ARG_ENABLE([installer],
+ AS_HELP_STRING([--enable-installer], [Build the graphical installer sources.]))
+
+AS_IF([test "x$enable_installer" = "xyes"], [
+if test "x$have_guile_newt" != "xyes"; then
+ AC_MSG_ERROR([Guile-newt could not be found; please install it.])
+fi
+])
+
+AM_CONDITIONAL([ENABLE_INSTALLER],
+ [test "x$enable_installer" = "xyes"])
+