diff --git a/anki/graphs.py b/anki/graphs.py
index 6105262b6..79788a10b 100644
--- a/anki/graphs.py
+++ b/anki/graphs.py
@@ -100,6 +100,8 @@ group by day order by day""" % (self._limit(), lim),
                                _("Review Time"))
 
     def _repsGraph(self, data, days, reptitle, timetitle):
+        if not data:
+            return ""
         d = data
         conf = dict(
             xaxis=dict(tickDecimals=0),