diff --git a/celestia/src/celengine/frametree.h b/celestia/src/celengine/frametree.h
index 2e1efa2..8ffff45 100644
--- a/celestia/src/celengine/frametree.h
+++ b/celestia/src/celengine/frametree.h
@@ -1,5 +1,4 @@
-// frametree.h
-//
+// frametree.h //
 // Reference frame tree.
 //
 // Copyright (C) 2008, the Celestia Development Team
@@ -14,6 +13,7 @@
 #define _CELENGINE_FRAMETREE_H_
 
 #include <vector>
+#include <libio.h>
 
 class Star;
 class Body;