diff --git a/tools/atree/fs.cpp b/tools/atree/fs.cpp
index 15d6092..022bd8c 100644
--- a/tools/atree/fs.cpp
+++ b/tools/atree/fs.cpp
@@ -6,6 +6,7 @@
 #include <string>
 #include <vector>
 #include <stdio.h>
+#include <string.h>
 #include <errno.h>
 #include <sys/stat.h>
 #include <unistd.h>