diff --git a/src/main.cc b/src/main.cc
index c542f23..ef14874 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -25,6 +25,7 @@
 #include <cstdlib>
 #include <fstream>
 #include <iostream>
+#include <unistd.h>
 #include <iterator>
 
 #include <exception>