diff --git a/M2/configure.ac b/M2/configure.ac
index fac9729c44..fb14355823 100644
--- a/M2/configure.ac
+++ b/M2/configure.ac
@@ -262,7 +262,7 @@ AC_SUBST(M2_CFLAGS)
 AC_SUBST(M2_CXXFLAGS)
 
 dnl Fix standards, apply everywhere
-CXXFLAGS="-std=gnu++14 $CXXFLAGS"
+CXXFLAGS="-std=gnu++17 $CXXFLAGS"
 CFLAGS="-std=gnu11 $CFLAGS"
 
 AC_PROG_CC() 			# set CFLAGS before this