diff --git a/espeak.c b/espeak.c
index 0aa6a62..f09d3c4 100644
--- a/espeak.c
+++ b/espeak.c
@@ -17,6 +17,7 @@
  *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#define _GNU_SOURCE
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>