diff --git a/lib/revision_stat_timeslice.rb b/lib/revision_stat_timeslice.rb
index aab0f429e3..ab74765fd0 100644
--- a/lib/revision_stat_timeslice.rb
+++ b/lib/revision_stat_timeslice.rb
@@ -7,7 +7,7 @@ class RevisionStatTimeslice
   def initialize(course, end_period = Time.zone.now)
     @course = course
     @end_period = end_period
-    @start_period = REVISION_TIMEFRAME.days.ago
+    @start_period = [REVISION_TIMEFRAME.days.ago, course.start].max
   end
 
   def recent_revisions_for_course