diff --git a/backends/frotz/dfrotz/common/input.c b/backends/frotz/dfrotz/common/input.c
index e4dad62d9e59a24c205e4eddb713c5fd7467db6b..62ff2c19ffca29daf6e9555ee13d694bd49728f1 100644
--- a/backends/frotz/dfrotz/common/input.c
+++ b/backends/frotz/dfrotz/common/input.c
@@ -21,6 +21,7 @@
 #include "frotz.h"
 
 extern int save_undo (void);
+extern int os_read_mouse (void);
 
 extern zchar stream_read_key (zword, zword, bool);
 extern zchar stream_read_input (int, zchar *, zword, zword, bool, bool);