diff --git a/FileUtils.h b/FileUtils.h
index 6f4e041cf0..47b11241a1 100644
--- a/FileUtils.h
+++ b/FileUtils.h
@@ -16,6 +16,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/fcntl.h>
+#include <unistd.h>
 #include <vector>
 
 using std::vector;