diff --git a/source/spyview/Gnuplot_Interface.H b/source/spyview/Gnuplot_Interface.H
index f15cb08..ef6fb2d 100644
--- a/spyview/Gnuplot_Interface.H
+++ b/spyview/Gnuplot_Interface.H
@@ -5,6 +5,7 @@
 #include <assert.h>
 #include <errno.h>
 #include <vector>
+#include <sys/types.h>
 #include "message.h"
 
 /* With the need for bi-directional communications with gnuplot,