diff --git a/meson.build b/meson.build
index 04b8094..624d85b 100644
--- a/meson.build
+++ b/meson.build
@@ -20,6 +20,7 @@
 )
 
 library_is_share = get_option('default_library') == 'shared'
+add_global_arguments('-D_POSIX_C_SOURCE=200809L', language : 'c')
 
 project_description = 'libcper library'