diff --git a/src/keyboard.c b/src/keyboard.c
index 0d56ea3f7ac..dccc6b7f128 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -12011,7 +12011,12 @@ mark_kboards (void)
     for (event = kbd_fetch_ptr; event != kbd_store_ptr; event++)
       {
 	if (event == kbd_buffer + KBD_BUFFER_SIZE)
-	  event = kbd_buffer;
+	  {
+	    event = kbd_buffer;
+	    if (event == kbd_store_ptr)
+	      break;
+	  }
+
 	/* These two special event types has no Lisp_Objects to mark.  */
 	if (event->kind != SELECTION_REQUEST_EVENT
 	    && event->kind != SELECTION_CLEAR_EVENT)