diff --git a/cartographer/mapping/map_builder.cc b/cartographer/mapping/map_builder.cc
index cc362ae..6c7109d 100644
--- a/cartographer/mapping/map_builder.cc
+++ b/cartographer/mapping/map_builder.cc
@@ -134,10 +134,6 @@ void MapBuilder::FinishTrajectory(const int trajectory_id) {
   pose_graph_->FinishTrajectory(trajectory_id);
 }
 
-int MapBuilder::GetBlockingTrajectoryId() const {
-  return sensor_collator_.GetBlockingTrajectoryId();
-}
-
 std::string MapBuilder::SubmapToProto(
     const mapping::SubmapId& submap_id,
     proto::SubmapQuery::Response* const response) {
diff --git a/cartographer/mapping/map_builder.h b/cartographer/mapping/map_builder.h
index b620252..4bd874d 100644
--- a/cartographer/mapping/map_builder.h
+++ b/cartographer/mapping/map_builder.h
@@ -77,11 +77,6 @@ class MapBuilder {
   // i.e. no further sensor data is expected.
   void FinishTrajectory(int trajectory_id);
 
-  // Must only be called if at least one unfinished trajectory exists. Returns
-  // the ID of the trajectory that needs more data before the MapBuilder is
-  // unblocked.
-  int GetBlockingTrajectoryId() const;
-
   // Fills the SubmapQuery::Response corresponding to 'submap_id'. Returns an
   // error string on failure, or an empty string on success.
   std::string SubmapToProto(const SubmapId& submap_id,