diff --git a/configure.ac b/configure.ac
index 87e49d590..106ed8a9f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -234,9 +234,9 @@ _MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_NEWEST,-std=c++03)
 AC_SUBST(CFG_CXXFLAGS_STD_NEWEST)
 # And likewise oldest standard (same list above, backwards)
 # This is used for internal testing
-_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=std++03)
-_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=std++11)
-_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=std++14)
+_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=c++03)
+_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=c++11)
+_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=c++14)
 #_MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=std++17)
 _MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=gnu++03)
 _MY_CXX_CHECK_SET(CFG_CXXFLAGS_STD_OLDEST,-std=gnu++11)