diff --git a/util/hb-subset.cc b/util/hb-subset.cc
index f5e8aaf3e..3dda92194 100644
--- a/util/hb-subset.cc
+++ b/util/hb-subset.cc
@@ -25,6 +25,8 @@
  * Google Author(s): Garret Rieger, Rod Sheeter
  */
 
+#include <unistd.h>
+
 #include "main-font-text.hh"
 
 /*