--- atop-2.12.1.orig/drawbar.c	2025-09-23 19:16:03.000000000 +0200
+++ atop-2.12.1/drawbar.c	2026-07-07 02:04:43.594438374 +0200
@@ -103,7 +103,7 @@
 // horizontally scaled by the user, atop might switch from one model to
 // the other.
 /////////////////////////////////////////////////////////////////////////////
-#define _POSIX_C_SOURCE
+#define _POSIX_C_SOURCE 200809L
 #define _XOPEN_SOURCE
 #define _GNU_SOURCE
 #define _DEFAULT_SOURCE
