diff --git a/meson.build b/meson.build
index 9d468862..36d1bafa 100644
--- a/meson.build
+++ b/meson.build
@@ -13,7 +13,8 @@ is_debug_build = get_option('buildtype').startswith('debug')
 cc = meson.get_compiler('c')
 
 add_project_arguments(
-  ['-D_GNU_SOURCE=200809L'] + (is_debug_build ? ['-D_DEBUG'] : []) +
+  ['-D_POSIX_C_SOURCE=200809L', '-D_GNU_SOURCE=200809L'] +
+  (is_debug_build ? ['-D_DEBUG'] : []) +
   cc.get_supported_arguments(
     ['-fstrict-aliasing',
      '-Wstrict-aliasing',