diff --git a/src/file.cc b/src/file.cc
index b3553106..438436cf 100644
--- a/src/file.cc
+++ b/src/file.cc
@@ -7,6 +7,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <cstring>