diff --git a/utils/tinygl.c b/utils/tinygl.c
index fab7f87..07d6eab 100644
--- a/utils/tinygl.c
+++ b/utils/tinygl.c
@@ -18,7 +18,7 @@ static font_t *font;
 static tinygl_text_mode_t text_mode = TINYGL_TEXT_MODE_STEP;
 static uint8_t message_index;
 static uint8_t scroll_pos = 0;
-static char message1[32] = "";
+static char message1[TINYGL_MESSAGE_SIZE] = "";
 
 
 /** Draw point.
diff --git a/utils/tinygl.h b/utils/tinygl.h
index 55d0ab9..185e50e 100644
--- a/utils/tinygl.h
+++ b/utils/tinygl.h
@@ -81,6 +81,10 @@
 #define TINYGL_HEIGHT DISPLAY_HEIGHT
 
 
+/** Maximum length of a message to display.  */
+#define TINYGL_MESSAGE_SIZE 32
+
+
 /** Define a pixel value.  Currently the only supported values are 0
     for off and 1 for on.  */
 typedef uint8_t tinygl_pixel_value_t;