diff --git a/examples/meson.build b/examples/meson.build
index 605fb8d83ab9d6fe9b8d40f0bbe9f3d7498a97c6..83af1519d55213073b5bed7d42dd816e93050245 100644
--- a/examples/meson.build
+++ b/examples/meson.build
@@ -25,9 +25,6 @@ executable(
   'steam-runtime-system-info',
   'system-info.c',
   dependencies : [glib, libsteamrt_dep, json_glib],
-  c_args : [
-      '-D_GNU_SOURCE',
-  ],
   install : true,
 )
 
diff --git a/helpers/check-gl.c b/helpers/check-gl.c
index 3d81ad9d472fbfdfb600a83418a8bfd7f84df8af..b2ac307f980ee27d2ff02988bd711aeec71b8a78 100644
--- a/helpers/check-gl.c
+++ b/helpers/check-gl.c
@@ -69,9 +69,6 @@
  * [3] http://git.compiz.org/fusion/misc/compiz-manager/tree/compiz-manager
  */
 
-/* for strcasestr */
-#define _GNU_SOURCE
-
 #include <ctype.h>
 #include <locale.h>
 #include <stdio.h>
diff --git a/helpers/check-gles.c b/helpers/check-gles.c
index e8571470d927ebd15fed41ffd961094bb12f3613..39192c8d2a025fddbad1a54c83e88c410ed0178c 100644
--- a/helpers/check-gles.c
+++ b/helpers/check-gles.c
@@ -23,9 +23,6 @@
  *   Cosimo Cecchi <cosimo@endlessm.com>
  */
 
-/* for strcasestr */
-#define _GNU_SOURCE
-
 #include <locale.h>
 #include <stdlib.h>
 #include <string.h>
diff --git a/helpers/meson.build b/helpers/meson.build
index dc993675d01675b187a717794d59e6322a2dd167..1e94285861befeafde76801ca04481cfdbdde85e 100644
--- a/helpers/meson.build
+++ b/helpers/meson.build
@@ -35,9 +35,6 @@ executable(
   multiarch + '-inspect-library',
   'inspect-library.c',
   dependencies : [libdl],
-  c_args : [
-      '-D_GNU_SOURCE',
-    ],
   install : true,
   install_dir : join_paths(
     get_option('libexecdir'),
diff --git a/meson.build b/meson.build
index dc8c9e606d1236bf0eb0e4b01d9f050ab318ab66..1a2c000cd0883282d5dc5577013ad5f411b41de4 100644
--- a/meson.build
+++ b/meson.build
@@ -91,6 +91,8 @@ endforeach
 
 add_project_arguments(['-std=c99'], language : 'c')
 
+add_project_arguments(['-D_GNU_SOURCE'], language : 'c')
+
 glib = dependency(
   'glib-2.0',
   version : '>= 2.32',
diff --git a/steam-runtime-tools/meson.build b/steam-runtime-tools/meson.build
index 1211aebc96a0134578611dec3caa341dfba1d525..5d3d0a0dccc5873c31f09f7652067e18b79537e6 100644
--- a/steam-runtime-tools/meson.build
+++ b/steam-runtime-tools/meson.build
@@ -56,7 +56,6 @@ libsteamrt = library(
   c_args : [
     '-DG_LOG_DOMAIN="' + meson.project_name() + '"',
     '-D_SRT_COMPILATION',
-    '-D_GNU_SOURCE',
     '-D_SRT_SONAME="libsteam-runtime-tools-' + api_major + '.so.' + abi_major + '"',
     '-D_SRT_MULTIARCH="' + multiarch + '"',
     '-D_SRT_API_MAJOR="' + api_major + '"',