diff --git a/src/anaglym.cc b/src/anaglym.cc
index 7610d34..d9f5eab 100644
--- a/src/anaglym.cc
+++ b/src/anaglym.cc
@@ -6,6 +6,7 @@
 #include <stdlib.h>                 /* exit(), srand() */
 #include <iostream>
 #include <string>
+#include <unistd.h>
 using namespace std;
 
 static void usage();