diff --git a/async.c b/async.c
index 8343df4..969353d 100644
--- a/async.c
+++ b/async.c
@@ -30,6 +30,7 @@
  */
 
 #include <string.h>
+#include <strings.h>
 #include <assert.h>
 #include <ctype.h>
 #include "async.h"