diff --git a/src/calibre/gui2/viewer/main.py b/src/calibre/gui2/viewer/main.py
index ccf215210c..4182897ee0 100644
--- a/src/calibre/gui2/viewer/main.py
+++ b/src/calibre/gui2/viewer/main.py
@@ -313,6 +313,8 @@ class EbookViewer(MainWindow, Ui_EbookViewer):
                 self.view.goto_bookmark(m)
             else:
                 self.pending_bookmark = bm
+                if spine_index < 0 or spine_index >= len(self.iterator.spine):
+                    spine_index = 0
                 self.load_path(self.iterator.spine[spine_index])
 
     def toc_clicked(self, index):