diff --git a/tools/iio/Makefile b/tools/iio/Makefile
index 83813ad379f9aa408109c160ad03d3e78c40f63a..bf7ae6d6612a1b86948781c1f2cf9c575e3c54bf 100644
--- a/tools/iio/Makefile
+++ b/tools/iio/Makefile
@@ -1,5 +1,5 @@
 CC = gcc
-CFLAGS = -Wall -g
+CFLAGS = -Wall -g -D_GNU_SOURCE
 
 all: iio_event_monitor lsiio generic_buffer
 
diff --git a/tools/iio/generic_buffer.c b/tools/iio/generic_buffer.c
index 01266c2556da995c6fe4a8d5ba4c95b42cbb7df0..8f8f058eb8074864e79e5327100241322df7f4e5 100644
--- a/tools/iio/generic_buffer.c
+++ b/tools/iio/generic_buffer.c
@@ -18,8 +18,6 @@
  *
  */
 
-#define _GNU_SOURCE
-
 #include <unistd.h>
 #include <stdlib.h>
 #include <dirent.h>
diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
index f19cff19900ec4d723cdf19cf9be9fda26a3cfde..427c271ac0d655988a54c30f475572927592916b 100644
--- a/tools/iio/iio_event_monitor.c
+++ b/tools/iio/iio_event_monitor.c
@@ -16,8 +16,6 @@
  *
  */
 
-#define _GNU_SOURCE
-
 #include <unistd.h>
 #include <stdlib.h>
 #include <stdbool.h>