diff -Naur CMakeLists.txt.orig CMakeLists.txt
--- a/CMakeLists.txt.orig
+++ b/CMakeLists.txt
@@ -106,9 +106,9 @@
 
 # use CPP-11
 if (CMAKE_VERSION VERSION_LESS "3.1")
-    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++20")
 else ()
-    set (CMAKE_CXX_STANDARD 11)
+    set (CMAKE_CXX_STANDARD 20)
 endif ()
 
 ############

