diff --git a/src/XlibInt.c b/src/XlibInt.c
index bab39bc00..31b6511cb 100644
--- a/src/XlibInt.c	
+++ b/src/XlibInt.c
@@ -45,6 +45,7 @@ from The Open Group.
 #include <stdio.h>
 #ifdef WIN32
 #include <direct.h>
+#include <io.h>
 #endif
 
 /* Needed for FIONREAD on Solaris */