diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index 1313e7fe..0b624717 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -1,4 +1,4 @@
-#define _POSIX_C_SOURCE 199309L
+#define _POSIX_C_SOURCE 200112L
 #include <assert.h>
 #include <drm_mode.h>
 #include <EGL/egl.h>
diff --git a/backend/multi/backend.c b/backend/multi/backend.c
index cefaa361..50851109 100644
--- a/backend/multi/backend.c
+++ b/backend/multi/backend.c
@@ -1,4 +1,4 @@
-#define _POSIX_C_SOURCE 199309L
+#define _POSIX_C_SOURCE 200112L
 #include <assert.h>
 #include <stdbool.h>
 #include <stdlib.h>