diff --git a/lib/event.h b/lib/event.h
index a347bb093..df6d857db 100644
--- a/lib/event.h
+++ b/lib/event.h
@@ -34,7 +34,7 @@ void mc_event_del (const gchar *, const gchar *, mc_event_callback_func_t, gpoin
 void mc_event_destroy (const gchar *, const gchar *);
 void mc_event_group_del (const gchar *);
 gboolean mc_event_present (const gchar *, const gchar *);
-gboolean mc_event_mass_add (event_init_t *, GError **);
+gboolean mc_event_mass_add (const event_init_t *, GError **);
 
 /* raise.c: */
 gboolean mc_event_raise (const gchar *, const gchar *, gpointer);
diff --git a/lib/event/event.c b/lib/event/event.c
index 2faf03751..8c5a6596e 100644
--- a/lib/event/event.c
+++ b/lib/event/event.c
@@ -92,7 +92,7 @@ mc_event_deinit (GError ** mcerror)
 /* --------------------------------------------------------------------------------------------- */
 
 gboolean
-mc_event_mass_add (event_init_t * events, GError ** mcerror)
+mc_event_mass_add (const event_init_t * events, GError ** mcerror)
 {
     size_t array_index;