diff --git a/include/sandboxfs.h b/include/sandboxfs.h
index f5213ac..8ea8cb7 100644
--- a/include/sandboxfs.h
+++ b/include/sandboxfs.h
@@ -26,5 +26,6 @@
 void sandbox_fs_close(void);
 int sandbox_fs_ls(const char *dirname);
 int fs_read_sandbox(const char *filename, void *buf, int offset, int len);
+int fs_write_sandbox(const char *filename, void *buf, int offset, int len);
 
 #endif