diff --git a/cartographer/mapping/map_builder.cc b/cartographer/mapping/map_builder.cc
index 528dbd4..3de42b8 100644
--- a/cartographer/mapping/map_builder.cc
+++ b/cartographer/mapping/map_builder.cc
@@ -37,7 +37,6 @@
 
 namespace cartographer {
 namespace mapping {
-
 namespace {
 
 using mapping::proto::SerializedData;
@@ -53,6 +52,25 @@ std::vector<std::string> SelectRangeSensorIds(
   return range_sensor_ids;
 }
 
+void MaybeAddPureLocalizationTrimmer(
+    const int trajectory_id,
+    const proto::TrajectoryBuilderOptions& trajectory_options,
+    PoseGraph* pose_graph) {
+  if (trajectory_options.pure_localization()) {
+    LOG(WARNING)
+        << "'TrajectoryBuilderOptions::pure_localization' field is deprecated. "
+           "Use 'TrajectoryBuilderOptions::pure_localization_trimmer' instead.";
+    pose_graph->AddTrimmer(common::make_unique<PureLocalizationTrimmer>(
+        trajectory_id, 3 /* max_submaps_to_keep */));
+    return;
+  }
+  if (trajectory_options.has_pure_localization_trimmer()) {
+    pose_graph->AddTrimmer(common::make_unique<PureLocalizationTrimmer>(
+        trajectory_id,
+        trajectory_options.pure_localization_trimmer().max_submaps_to_keep()));
+  }
+}
+
 }  // namespace
 
 proto::MapBuilderOptions CreateMapBuilderOptions(
@@ -147,11 +165,9 @@ int MapBuilder::AddTrajectoryBuilder(
           trimmer_options.min_added_submaps_count()));
     }
   }
-  if (trajectory_options.has_pure_localization_trimmer()) {
-    pose_graph_->AddTrimmer(common::make_unique<PureLocalizationTrimmer>(
-        trajectory_id,
-        trajectory_options.pure_localization_trimmer().max_submaps_to_keep()));
-  }
+  MaybeAddPureLocalizationTrimmer(trajectory_id, trajectory_options,
+                                  pose_graph_.get());
+
   if (trajectory_options.has_initial_trajectory_pose()) {
     const auto& initial_trajectory_pose =
         trajectory_options.initial_trajectory_pose();
diff --git a/cartographer/mapping/proto/trajectory_builder_options.proto b/cartographer/mapping/proto/trajectory_builder_options.proto
index b996cb3..52747bb 100644
--- a/cartographer/mapping/proto/trajectory_builder_options.proto
+++ b/cartographer/mapping/proto/trajectory_builder_options.proto
@@ -38,6 +38,7 @@ message TrajectoryBuilderOptions {
   }
   OverlappingSubmapsTrimmerOptions2D overlapping_submaps_trimmer_2d = 5;
 
+  bool pure_localization = 3 [deprecated = true];
   message PureLocalizationTrimmerOptions {
     int32 max_submaps_to_keep = 1;
   }