diff --git a/sys/teken/demo/teken_demo.c b/sys/teken/demo/teken_demo.c
index 08323dc1a40..42747ce36b9 100644
--- a/sys/teken/demo/teken_demo.c
+++ b/sys/teken/demo/teken_demo.c
@@ -72,7 +72,7 @@ struct pixel {
 
 #define NCOLS	80
 #define NROWS	24
-struct pixel buffer[NCOLS][NROWS];
+static struct pixel buffer[NCOLS][NROWS];
 
 static int ptfd;