diff --git a/platformio.ini b/platformio.ini
index faf4fd9a..da5ca523 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -27,10 +27,7 @@ build_flags =
 # https://libexpat.github.io/doc/api/latest/#XML_GE
   -DXML_GE=0
   -DXML_CONTEXT_BYTES=1024
-  ; -std=c++2a
-  -std=gnu++2a
-
-build_unflags = -std=gnu++11
+  -std=c++2a
 
 # Enable UTF-8 long file names in SdFat
   -DUSE_UTF8_LONG_NAMES=1