diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index ffac20e..9f6775f 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -5421,9 +5421,9 @@
  */
     static void
 sniff_request_cb(
-    gpointer	data,
-    gint	source_fd,
-    GdkInputCondition condition)
+    gpointer	data UNUSED,
+    gint	source_fd UNUSED,
+    GdkInputCondition condition UNUSED)
 {
     static char_u bytes[3] = {CSI, (int)KS_EXTRA, (int)KE_SNIFF};