diff --git a/newlib/libc/stdlib/wcstold.c b/newlib/libc/stdlib/wcstold.c
index c57def21d..4876e119b 100644
--- a/newlib/libc/stdlib/wcstold.c
+++ b/newlib/libc/stdlib/wcstold.c
@@ -28,6 +28,7 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
 */
 
+#define _GNU_SOURCE
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>