diff --git a/src/main/java/org/opentripplanner/model/TimetableSnapshot.java b/src/main/java/org/opentripplanner/model/TimetableSnapshot.java
index 5c018412572..63bef21cfac 100644
--- a/src/main/java/org/opentripplanner/model/TimetableSnapshot.java
+++ b/src/main/java/org/opentripplanner/model/TimetableSnapshot.java
@@ -330,10 +330,23 @@ public boolean revertTripToScheduledTripPattern(FeedScopedId tripId, LocalDate s
         }
 
         if (tripTimesToRemove != null) {
-          for (Timetable sortedTimetable : sortedTimetables) {
-            boolean isDirty = sortedTimetable.getTripTimes().remove(tripTimesToRemove);
+          for (Timetable originalTimetable : sortedTimetables) {
+            boolean isDirty = originalTimetable.getTripTimes().contains(tripTimesToRemove);
             if (isDirty) {
-              dirtyTimetables.add(sortedTimetable);
+              Timetable updatedTimetable;
+              if (dirtyTimetables.contains(originalTimetable)) {
+                // the timetable has already been copied-on-write in this snapshot
+                // no need to copy it again
+                updatedTimetable = originalTimetable;
+              } else {
+                // create a copy of this timetable and swap the copy and the original
+                updatedTimetable = new Timetable(originalTimetable, serviceDate);
+                sortedTimetables.remove(originalTimetable);
+                sortedTimetables.add(updatedTimetable);
+                dirtyTimetables.add(updatedTimetable);
+                dirty = true;
+              }
+              updatedTimetable.getTripTimes().remove(tripTimesToRemove);
             }
           }
         }