--- atop-2.12.1.orig/atop.c	2025-09-23 19:16:03.000000000 +0200
+++ atop-2.12.1/atop.c	2026-07-07 02:02:15.281022186 +0200
@@ -118,7 +118,7 @@
 ** can be linked with 'atop'; the one to use can eventually be chosen
 ** at runtime. 
 */
-#define _POSIX_C_SOURCE	
+#define _POSIX_C_SOURCE	200809L
 #define _XOPEN_SOURCE
 #define _GNU_SOURCE
 #define _DEFAULT_SOURCE
