--- configure.in.orig	2014-07-18 10:11:43.000000000 -0500
+++ configure.in	2015-03-29 20:18:03.000000000 -0500
@@ -102,12 +102,12 @@
 fi
 AC_MSG_CHECKING(version of guile)
 if test -z "$GUILE_EFFECTIVE_VERSION" ; then
-  GUILE_EFFECTIVE_VERSION=`guile -c '(display (version))'`
+  GUILE_EFFECTIVE_VERSION=`guile18 -c '(display (version))'`
 fi
 AC_MSG_RESULT($GUILE_EFFECTIVE_VERSION)
 AC_MSG_CHECKING(guile data path)
 if test -z "$GUILE_DATA_PATH" ; then
-  GUILE_DATA_PATH=`guile-config info pkgdatadir`
+  GUILE_DATA_PATH=`guile18-config info pkgdatadir`
 fi
 AC_MSG_RESULT($GUILE_DATA_PATH)
 
@@ -596,14 +596,15 @@
 #--------------------------------------------------------------------
 
 AC_MSG_CHECKING(whether ... arguments behave correctly)
+SAVE_CXXFLAGS="$CXXFLAGS"
 if test -z "$GUILE_CFLAGS"; then
-  CXXFLAGS="`guile-config compile`"
+  CXXFLAGS="`guile18-config compile`"
 else
   CXXFLAGS="$GUILE_CFLAGS"
 fi
 AC_TRY_COMPILE([
-  #include <guile/gh.h>
-  #include <libguile.h>
+  #include <guile18/gh.h>
+  #include <libguile18.h>
   typedef SCM (*FN)(...);
   static SCM identity (SCM x) { return x; }
   void declare () { gh_new_procedure ("identity", (FN) identity, 1, 0, 0); }
@@ -614,17 +615,16 @@
 ],[
   AC_MSG_RESULT(no)
 ])
-CXXFLAGS=""
 
 AC_MSG_CHECKING(the size_t of guile strings)
 if test -z "$GUILE_CFLAGS"; then
-  CXXFLAGS="`guile-config compile`"
+  CXXFLAGS="`guile18-config compile`"
 else
   CXXFLAGS="$GUILE_CFLAGS"
 fi
 AC_TRY_COMPILE([
-  #include <guile/gh.h>
-  #include <libguile.h>
+  #include <guile18/gh.h>
+  #include <libguile18.h>
   void print_string (SCM s) {
     int len_r;
     char* r= gh_scm2newstr (s, &len_r); }
@@ -636,7 +636,7 @@
   AC_DEFINE(guile_str_size_t, size_t, [Guile string size type])
   AC_MSG_RESULT(size_t)
 ])
-CXXFLAGS=""
+CXXFLAGS="$SAVE_CXXFLAGS"
 
 AC_MSG_CHECKING([if statically linking with guile works])
 SAVE_CPPFLAGS="$CPPFLAGS"
@@ -1178,6 +1178,7 @@
     STD_DEBUG_FLAGS=""
 fi
 
+SAVE_CXXFLAGS="$CXXFLAGS"
 AC_MSG_CHECKING(if compiler supports $STD_DEBUG_FLAGS)
 CXXFLAGS="$STD_DEBUG_FLAGS"
 AC_TRY_COMPILE([
@@ -1190,7 +1191,7 @@
     CONFIG_CXXDIALECT=""
     AC_MSG_RESULT(no)
 ])
-CXXFLAGS=""
+CXXFLAGS="$SAVE_CXXFLAGS"
 AC_SUBST(CONFIG_CXXDIALECT)
 
 AC_ARG_ENABLE(profile,