diff --git a/intro/io.c b/intro/io.c
index 617fd4d..6d9385d 100644
--- a/intro/io.c
+++ b/intro/io.c
@@ -2,6 +2,7 @@
 #include <unistd.h>
 #include <assert.h>
 #include <fcntl.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 #include <string.h>