diff --git a/man/event-quick-child.c b/man/event-quick-child.c
index b95ee1bef6..828f0cd6f4 100644
--- a/man/event-quick-child.c
+++ b/man/event-quick-child.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: MIT-0 */
 
+#define _GNU_SOURCE 1
 #include <assert.h>
 #include <stdio.h>
 #include <unistd.h>
diff --git a/man/hwdb-usb-device.c b/man/hwdb-usb-device.c
index facd8c43b2..3ce3ccd87f 100644
--- a/man/hwdb-usb-device.c
+++ b/man/hwdb-usb-device.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: MIT-0 */
 
+#define _GNU_SOURCE 1
 #include <stdio.h>
 #include <stdint.h>
 #include <systemd/sd-hwdb.h>
diff --git a/man/journal-iterate-poll.c b/man/journal-iterate-poll.c
index d377324b78..6b78296267 100644
--- a/man/journal-iterate-poll.c
+++ b/man/journal-iterate-poll.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: MIT-0 */
 
+#define _GNU_SOURCE 1
 #include <poll.h>
 #include <time.h>
 #include <systemd/sd-journal.h>
diff --git a/man/journal-stream-fd.c b/man/journal-stream-fd.c
index c70d7986b2..595091af81 100644
--- a/man/journal-stream-fd.c
+++ b/man/journal-stream-fd.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: MIT-0 */
 
+#define _GNU_SOURCE 1
 #include <errno.h>
 #include <syslog.h>
 #include <stdio.h>
diff --git a/man/meson.build b/man/meson.build
index 22ac236b27..a728fa3384 100644
--- a/man/meson.build
+++ b/man/meson.build
@@ -306,10 +306,10 @@ default_args = [
 ]
 
 std_args_in = [
-        [ '-std=c99', '-D_GNU_SOURCE', ],
-        [ '-std=c11', '-D_GNU_SOURCE', ],
-        [ '-std=c17', '-D_GNU_SOURCE', ],
-        [ '-std=c23', '-D_GNU_SOURCE', ],
+        [ '-std=c99', ],
+        [ '-std=c11', ],
+        [ '-std=c17', ],
+        [ '-std=c23', ],
         [ '-std=gnu99', ],
         [ '-std=gnu11', ],
         [ '-std=gnu17', ],
diff --git a/man/notify-selfcontained-example.c b/man/notify-selfcontained-example.c
index 39f0dbe3fd..90c3861374 100644
--- a/man/notify-selfcontained-example.c
+++ b/man/notify-selfcontained-example.c
@@ -7,6 +7,7 @@
  * This protocol is guaranteed to be stable as per:
  * https://systemd.io/PORTABILITY_AND_STABILITY/ */
 
+#define _GNU_SOURCE 1
 #include <errno.h>
 #include <inttypes.h>
 #include <signal.h>
diff --git a/man/vtable-example.c b/man/vtable-example.c
index 417ee0ccf1..2e8994471a 100644
--- a/man/vtable-example.c
+++ b/man/vtable-example.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: MIT-0 */
 
+#define _GNU_SOURCE 1
 #include <errno.h>
 #include <stdbool.h>
 #include <stddef.h>