Index: simgear/misc/sg_path.cxx
--- simgear/misc/sg_path.cxx.orig
+++ simgear/misc/sg_path.cxx
@@ -33,6 +33,7 @@
 #include <stdio.h>
 #include <sys/stat.h>
 #include <errno.h>
+#include <unistd.h>
 #include <fstream>
 #include <cstdlib>
 
