diff --git a/openbsd-compat/freezero.c b/openbsd-compat/freezero.c
index 3af8f4a7..7f6bc7fa 100644
--- a/openbsd-compat/freezero.c
+++ b/openbsd-compat/freezero.c
@@ -14,6 +14,7 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <string.h>
 #include "includes.h"
 
 #ifndef HAVE_FREEZERO