diff --git a/vmstat.c b/vmstat.c
index 600f136..c22f735 100644
--- a/vmstat.c
+++ b/vmstat.c
@@ -34,6 +34,7 @@
 #include <stdlib.h>
 #include <sys/param.h>
 #include <unistd.h>
+#include <string.h>
 
 struct state {
     long procs_r;