diff --git a/configure.ac b/configure.ac
index 8e8ad57..4050c66 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,7 +37,7 @@
 )
 
 # Checks for typedefs, structures, and compiler characteristics.
-AX_CXX_COMPILE_STDCXX_17([noext])
+AX_CXX_COMPILE_STDCXX([20],[noext])
 AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CXXFLAGS])
 
 # Checks for libraries.