Index: lemonbar.c
--- lemonbar.c.orig
+++ lemonbar.c
@@ -1,5 +1,4 @@
 // vim:sw=4:ts=4:et:
-#define _POSIX_C_SOURCE 200809L
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -1503,6 +1502,11 @@ main (int argc, char **argv)
     free(wm_name);
     // Get the fd to Xserver
     pollin[1].fd = xcb_get_file_descriptor(c);
+
+    if (pledge("stdio", NULL) == -1) {
+        fprintf(stderr, "pledge: %s\n", strerror(errno));
+        return EXIT_FAILURE;
+    }
 
     for (;;) {
         bool redraw = false;