diff --git a/adat/adat.c b/adat/adat.c
index f6e8d8ea9..b6e50e613 100644
--- a/adat/adat.c
+++ b/adat/adat.c
@@ -21,6 +21,7 @@
 //   License along with this library; if not, write to the Free Software
 //   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #  include "config.h"
diff --git a/aor/ar3030.c b/aor/ar3030.c
index bc03c253c..a3d3bd18a 100644
--- a/aor/ar3030.c
+++ b/aor/ar3030.c
@@ -18,6 +18,7 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
diff --git a/barrett/barrett.c b/barrett/barrett.c
index a0c39c145..69459fa71 100644
--- a/barrett/barrett.c
+++ b/barrett/barrett.c
@@ -18,6 +18,8 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
+
 #ifdef HAVE_CONFIG_H
 #  include "config.h"
 #endif
diff --git a/dummy/dummy.c b/dummy/dummy.c
index f42b0b0af..f46fb3c25 100644
--- a/dummy/dummy.c
+++ b/dummy/dummy.c
@@ -19,6 +19,7 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
diff --git a/dummy/flrig.c b/dummy/flrig.c
index 2b84d460f..d7ee4d5b5 100644
--- a/dummy/flrig.c
+++ b/dummy/flrig.c
@@ -19,6 +19,8 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
+
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
diff --git a/elad/elad.c b/elad/elad.c
index 648e42004..01f56a26a 100644
--- a/elad/elad.c
+++ b/elad/elad.c
@@ -21,6 +21,7 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
diff --git a/icom/optoscan.c b/icom/optoscan.c
index 0f05d6aec..d733286a6 100644
--- a/icom/optoscan.c
+++ b/icom/optoscan.c
@@ -18,6 +18,7 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
diff --git a/kenwood/kenwood.c b/kenwood/kenwood.c
index 7bf9794fb..f2fd87935 100644
--- a/kenwood/kenwood.c
+++ b/kenwood/kenwood.c
@@ -20,6 +20,7 @@
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
diff --git a/pcr/pcr.c b/pcr/pcr.c
index f4422aa8a..299be8b74 100644
--- a/pcr/pcr.c
+++ b/pcr/pcr.c
@@ -28,6 +28,7 @@
  * (403) PCR1500 fw 2.0, proto 2.0 (usb) by KM3T
  *
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
diff --git a/tentec/orion.c b/tentec/orion.c
index 241c14d40..c652d13ea 100644
--- a/tentec/orion.c
+++ b/tentec/orion.c
@@ -65,6 +65,7 @@
  * This backend supports the Ten-Tec Orion (565) and Orion II (566) transceivers.
  * \n This backend tested mostly with firmware versions 1.372 and 2.062a
  */
+#define _XOPEN_SOURCE 500
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"