--- xdrawchem-1.9.9/xdrawchem/application.cpp.compile	2005-11-16 12:01:55.000000000 +0900
+++ xdrawchem-1.9.9/xdrawchem/application.cpp	2012-08-01 15:57:31.545768999 +0900
@@ -14,6 +14,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
+#include <unistd.h>
 
 using std::cout;
 using std::endl;