diff --git a/configure.ac b/configure.ac
--- a/configure.ac
+++ b/configure.ac
@@ -1,82 +1,83 @@
 dnl Process this file with autoconf to produce a configure script.
 dnl
 
 AC_PREREQ([2.59])
 AC_INIT(Dummy,0.0)
 AC_CONFIG_AUX_DIR([Config])
 AC_CONFIG_MACRO_DIR([m4])
 THEPEG_LIBTOOL_VERSION_INFO(3,0,0)
 AM_INIT_AUTOMAKE([1.9 gnu dist-bzip2 -Wall])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
 AC_LANG(C++)
 
 dnl Checks for programs.
 AC_PROG_CXX
+AX_CXX_COMPILE_STDCXX([11],[noext],[mandatory])
 AC_PROG_INSTALL
 AC_PROG_MAKE_SET #???
 AC_PROG_LN_S
 
 LT_PREREQ([2.2])
 LT_INIT([disable-static dlopen pic-only])
 
 THEPEG_SEARCH_LHAPDF
 
 THEPEG_SEARCH_HEPMC
 
 THEPEG_SEARCH_THEPEG
 
 THEPEG_ADD_THEPEG_PATH(PYTHIA7LIBPATH,Pythia7)
 
 AC_PROG_FC
 AC_FC_LIBRARY_LDFLAGS
 AC_MSG_CHECKING([if HZTool is present and works])
 if test "x$HZTOOLDIR" == "x"; then
   HZTOOLDIR="/usr/local/lib"
 fi
 if test "x$CERNLIBDIR" == "x"; then
   if test -d /usr/local/cern/lib; then
     CERNLIBDIR="/usr/local/cern/lib"
   else
     CERNLIBDIR="/usr/local/lib"
   fi
 fi
 oldLIB="$LIBS"
 oldLDFLAGS="$LDFLAGS"
 LIBS="$LIBS -lhztool -lkernlib -lmathlib -lpacklib $FCLIBS"		
 LDFLAGS="$LDFLAGS -L$HZTOOLDIR -L$CERNLIBDIR"
 AC_LINK_IFELSE([AC_LANG_PROGRAM([[extern "C" { void hzh9807018_(const int&); void structm_() {} void pdfset_() {} void lulist_() {} void pylist_() {} void luexec_() {} void kpisflag_() {} }]],
                                   [[hzh9807018_(1);]])], HAS_HZTOOL="yes",
                                   HAS_HZTOOL="no")
 if test "$HAS_HZTOOL" == "yes"; then
   HZTOOL_LIBS="-lhztool -lkernlib -lmathlib -lpacklib $FCLIBS"
   HZTOOL_LDFLAGS=" -L$HZTOOLDIR -L$CERNLIBDIR"
   AC_DEFINE(ThePEG_HAS_HZTOOL, 1, [Set if HZTOOL is present and working])
   AC_SUBST(HZTOOL_LIBS, [], [Libraries needed for HZTOOL])
   AC_SUBST(HZTOOL_LDFLAGS, [], [Link flags needed for HZTOOL])
   AC_MSG_RESULT([yes])
 else
   AC_MSG_RESULT([no])
 fi
 LIBS="$oldLIB"
 LDFLAGS="$oldLDFLAGS"
 AM_CONDITIONAL([USEHZTOOL], [test "x$HAS_HZTOOL" == "xyes"])
 
 
 
 AC_SUBST([F77],[$FC])
 THEPEG_EMPTY_SUBST
 
-AM_CXXFLAGS="-ansi -pedantic -Wall"
+AM_CXXFLAGS="-pedantic -Wall"
 AC_SUBST(AM_CXXFLAGS)
 
 AC_CONFIG_FILES([Misc/Makefile
 Decay/Makefile
 LesHouches/Makefile
 HZTOOL/Makefile
 Analysis/Makefile
 Makefile])
 ## don't know what to do here  'Doc/Makefile'
 
 AC_OUTPUT