diff --git a/cartographer/mapping_2d/sparse_pose_graph.cc b/cartographer/mapping_2d/sparse_pose_graph.cc
index 6211d8e..8263704 100644
--- a/cartographer/mapping_2d/sparse_pose_graph.cc
+++ b/cartographer/mapping_2d/sparse_pose_graph.cc
@@ -118,8 +118,8 @@ void SparsePoseGraph::AddScan(
     submap_states_.emplace_back();
     submap_states_.back().submap = insertion_submaps.back();
     submap_states_.back().id = mapping::SubmapId{
-        trajectory_id, num_submaps_in_trajectory_[trajectory]};
-    ++num_submaps_in_trajectory_[trajectory];
+        trajectory_id, num_submaps_in_trajectory_[trajectory_id]};
+    ++num_submaps_in_trajectory_[trajectory_id];
     CHECK_EQ(submap_states_.size(), submap_indices_.size());
   }
   const mapping::Submap* const finished_submap =
diff --git a/cartographer/mapping_2d/sparse_pose_graph.h b/cartographer/mapping_2d/sparse_pose_graph.h
index 549767c..48c78a2 100644
--- a/cartographer/mapping_2d/sparse_pose_graph.h
+++ b/cartographer/mapping_2d/sparse_pose_graph.h
@@ -198,8 +198,7 @@ class SparsePoseGraph : public mapping::SparsePoseGraph {
   // before they take part in the background computations.
   std::map<const mapping::Submap*, int> submap_indices_ GUARDED_BY(mutex_);
   std::vector<SubmapState> submap_states_ GUARDED_BY(mutex_);
-  std::map<const mapping::Submaps*, int> num_submaps_in_trajectory_
-      GUARDED_BY(mutex_);
+  std::map<int, int> num_submaps_in_trajectory_ GUARDED_BY(mutex_);
 
   // Connectivity structure of our trajectories by IDs.
   std::vector<std::vector<int>> connected_components_;
diff --git a/cartographer/mapping_3d/sparse_pose_graph.cc b/cartographer/mapping_3d/sparse_pose_graph.cc
index 4f69078..40dcad6 100644
--- a/cartographer/mapping_3d/sparse_pose_graph.cc
+++ b/cartographer/mapping_3d/sparse_pose_graph.cc
@@ -115,8 +115,8 @@ void SparsePoseGraph::AddScan(
     submap_states_.emplace_back();
     submap_states_.back().submap = insertion_submaps.back();
     submap_states_.back().id = mapping::SubmapId{
-        trajectory_id, num_submaps_in_trajectory_[trajectory]};
-    ++num_submaps_in_trajectory_[trajectory];
+        trajectory_id, num_submaps_in_trajectory_[trajectory_id]};
+    ++num_submaps_in_trajectory_[trajectory_id];
     CHECK_EQ(submap_states_.size(), submap_indices_.size());
   }
   const Submap* const finished_submap =
diff --git a/cartographer/mapping_3d/sparse_pose_graph.h b/cartographer/mapping_3d/sparse_pose_graph.h
index 3bddd63..274fc29 100644
--- a/cartographer/mapping_3d/sparse_pose_graph.h
+++ b/cartographer/mapping_3d/sparse_pose_graph.h
@@ -198,8 +198,7 @@ class SparsePoseGraph : public mapping::SparsePoseGraph {
   // before they take part in the background computations.
   std::map<const mapping::Submap*, int> submap_indices_ GUARDED_BY(mutex_);
   std::vector<SubmapState> submap_states_ GUARDED_BY(mutex_);
-  std::map<const mapping::Submaps*, int> num_submaps_in_trajectory_
-      GUARDED_BY(mutex_);
+  std::map<int, int> num_submaps_in_trajectory_ GUARDED_BY(mutex_);
 
   // Connectivity structure of our trajectories by IDs.
   std::vector<std::vector<int>> connected_components_;