diff --git a/configure.ac b/configure.ac
index 712ca0abd..c6eb76c18 100644
--- a/configure.ac
+++ b/configure.ac
@@ -340,6 +340,7 @@ PLATCXXFLAGS="$PLATCFLAGS"
 if test x"$enable_cpp11_testing" = xyes; then
   AC_LANG_PUSH([C++])
   CXXFLAGS_SAVED=$CXXFLAGS
+  CXXFLAGS=
   AX_CXX_COMPILE_STDCXX_11([noext], [nostop])
   CXXFLAGS=$CXXFLAGS_SAVED
   AC_LANG_POP([C++])