diff --git a/src/calibre/ebooks/lrf/objects.py b/src/calibre/ebooks/lrf/objects.py
index 7c9cbdf45e..38d1893eed 100644
--- a/src/calibre/ebooks/lrf/objects.py
+++ b/src/calibre/ebooks/lrf/objects.py
@@ -1013,6 +1013,7 @@ class Button(LRFObject):
         for i in self.actions[button_type]:
             if i[0] == 1:
                 return i[1:][0]
+        return (None, None)
     
     def __unicode__(self):
         s = u'<Button objid="%s">\n'%(self.id,)
diff --git a/src/calibre/gui2/lrf_renderer/document.py b/src/calibre/gui2/lrf_renderer/document.py
index c0edb37b15..5bc72b3630 100644
--- a/src/calibre/gui2/lrf_renderer/document.py
+++ b/src/calibre/gui2/lrf_renderer/document.py
@@ -366,7 +366,7 @@ class Document(QGraphicsScene):
     def get_page_num(self, chapterid, objid):
         cnum = self.chapter_map[chapterid]
         page = self.chapters[cnum].object_to_page_map[objid]
-        return sum(self.chapter_layout[:cnum])+page        
+        return sum(self.chapter_layout[:cnum])+page
     
     def add_to_history(self):
         page = self.chapter_page(self.current_page)[1]
@@ -377,9 +377,10 @@ class Document(QGraphicsScene):
     def link_activated(self, objid, on_creation=None):
         if on_creation is None:
             cid, oid = self.link_map[objid]
-            self.add_to_history()
-            page = self.get_page_num(cid, oid)
-            self.show_page(page) 
+            if oid is not None:
+                self.add_to_history()
+                page = self.get_page_num(cid, oid)
+                self.show_page(page)
         else:
             jb = self.objects[objid]
             self.link_map[objid] = (jb.refpage, jb.refobj)
@@ -539,4 +540,4 @@ class Document(QGraphicsScene):
         else:
             self.add_to_history()
             self.show_page(page_num)
-        
\ No newline at end of file
+        
diff --git a/src/calibre/gui2/lrf_renderer/main.py b/src/calibre/gui2/lrf_renderer/main.py
index 30a6a8597d..c056ac1053 100644
--- a/src/calibre/gui2/lrf_renderer/main.py
+++ b/src/calibre/gui2/lrf_renderer/main.py
@@ -228,6 +228,12 @@ class Main(MainWindow, Ui_MainWindow):
     def back(self, triggered):
         self.document.back()
         
+    def wheelEvent(self, ev):
+        if ev.delta() >= 0:
+            self.document.previous()
+        else:
+            self.document.next()
+
     def closeEvent(self, event):
         if self.renderer is not None and self.renderer.isRunning():
             self.renderer.abort()