diff --git a/src/psl.c b/src/psl.c
index 9fa6aab..7b6d7f0 100644
--- a/src/psl.c
+++ b/src/psl.c
@@ -64,6 +64,7 @@ typedef SSIZE_T ssize_t;
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <ctype.h>
 #include <time.h>
 #include <errno.h>