diff --git a/src/disk_interface.cc b/src/disk_interface.cc
index 28530b1..4da9a38 100644
--- a/src/disk_interface.cc
+++ b/src/disk_interface.cc
@@ -21,6 +21,7 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <unistd.h>
 
 #ifdef _WIN32
 #include <sstream>