More missing const
diff --git a/contiki/ctk/ctk.h b/contiki/ctk/ctk.h
index 3617a56..6c25356 100644
--- a/contiki/ctk/ctk.h
+++ b/contiki/ctk/ctk.h
@@ -233,6 +233,7 @@
 	do { memset((e)->text, 0, (e)->h * ((e)->len + 1)); \
 	     (e)->xpos = 0; (e)->ypos = 0; } while(0)
 
+struct ctk_textentry;
 typedef unsigned char (* ctk_textentry_input)(ctk_arch_key_t c,
 					      struct ctk_textentry *t);