diff --git a/meson.build b/meson.build
index d26c68d..6b097b0 100644
--- a/meson.build
+++ b/meson.build
@@ -21,5 +21,6 @@ deps = [libssl, libyaml, libcyaml, libmath, libmyclib]
 
 add_global_arguments('-DUSE_COLORS', language: 'c')
 add_global_arguments('-DEVELOPER', language: 'c')
+add_global_arguments('-D_POSIX_C_SOURCE=200112L', language: 'c')
 
 executable('cws', server, include_directories: incdir, dependencies: deps)