diff --git a/src/client/libdistren.h b/src/client/libdistren.h
--- a/src/client/libdistren.h
+++ b/src/client/libdistren.h
@@ -17,6 +17,9 @@
   along with DistRen.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#ifndef LIBDISTREN_H_
+#define LIBDISTREN_H_ 1
+
 /*
   Private definitions for libdistren.
  */
@@ -68,3 +71,6 @@ int _distren_getoptions(distren_t handle
    Unsets-up the distren handle with options loadable from a config file.
  */
 int _distren_loseoptions(distren_t handle);
+
+#endif
+