diff --git a/configure.ac b/configure.ac
index 6d3c2846..e194542b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -52,7 +52,7 @@ AC_PROG_CC_C99
 AC_PROG_INSTALL
 AC_HEADER_STDC
 
-AX_CXX_COMPILE_STDCXX_14(,[mandatory])
+AX_CXX_COMPILE_STDCXX_14
 AX_COMPILER_FLAGS(,,[yes])
 AX_VALGRIND_CHECK