diff --git a/configure.ac b/configure.ac
index 82d7d8a..d30af1f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -26,7 +26,7 @@
 AC_PROG_MAKE_SET
 
 # Checks for typedefs, structures, and compiler characteristics.
-AX_CXX_COMPILE_STDCXX_17([noext])
+AX_CXX_COMPILE_STDCXX([20],[noext])
 AX_APPEND_COMPILE_FLAGS([-fpic -Wall -Werror], [CXXFLAGS])
 
 # Checks for libraries.