diff --git a/ClanLib/Sources/Core/IOData/Generic/inputsource_file.cpp b/ClanLib/Sources/Core/IOData/Generic/inputsource_file.cpp
index d0413e5..7b3da2a 100644
--- a/ClanLib/Sources/Core/IOData/Generic/inputsource_file.cpp
+++ b/ClanLib/Sources/Core/IOData/Generic/inputsource_file.cpp
@@ -27,6 +27,8 @@
 **    (if your name is missing here, please add it)
 */
 
+#include <unistd.h>
+
 #include "Core/precomp.h"
 
 #ifdef WIN32