diff --git a/cartographer_grpc/internal/handlers/add_fixed_frame_pose_data_handler_test.cc b/cartographer_grpc/internal/handlers/add_fixed_frame_pose_data_handler_test.cc
index 2551695..88e9941 100644
--- a/cartographer_grpc/internal/handlers/add_fixed_frame_pose_data_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/add_fixed_frame_pose_data_handler_test.cc
@@ -30,7 +30,7 @@ using ::testing::Eq;
 using ::testing::Pointee;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
   sensor_metadata {
     trajectory_id: 1
     sensor_id: "sensor_id"
@@ -45,7 +45,7 @@ const std::string kMessage = R"PROTO(
         w: 6 x: 7 y: 8 z: 9
       }
     }
-  })PROTO";
+  })";
 
 using AddFixedFramePoseDataHandlerTest =
     testing::HandlerTest<AddFixedFramePoseDataHandler>;
diff --git a/cartographer_grpc/internal/handlers/add_imu_data_handler_test.cc b/cartographer_grpc/internal/handlers/add_imu_data_handler_test.cc
index bbadd94..4dc4b97 100644
--- a/cartographer_grpc/internal/handlers/add_imu_data_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/add_imu_data_handler_test.cc
@@ -30,7 +30,7 @@ using ::testing::Eq;
 using ::testing::Pointee;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
   sensor_metadata {
     trajectory_id: 1
     sensor_id: "sensor_id"
@@ -43,7 +43,7 @@ const std::string kMessage = R"PROTO(
     angular_velocity {
       x: 6 y: 7 z: 8
     }
-  })PROTO";
+  })";
 
 using AddImuDataHandlerTest = testing::HandlerTest<AddImuDataHandler>;
 
diff --git a/cartographer_grpc/internal/handlers/add_landmark_data_handler_test.cc b/cartographer_grpc/internal/handlers/add_landmark_data_handler_test.cc
index a9dd633..ea46948 100644
--- a/cartographer_grpc/internal/handlers/add_landmark_data_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/add_landmark_data_handler_test.cc
@@ -30,7 +30,7 @@ using ::testing::Eq;
 using ::testing::Pointee;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
   sensor_metadata {
     trajectory_id: 1
     sensor_id: "sensor_id"
@@ -50,7 +50,7 @@ const std::string kMessage = R"PROTO(
       translation_weight: 11.0
       rotation_weight: 12.0
     }
-  })PROTO";
+  })";
 
 using AddLandmarkDataHandlerTest = testing::HandlerTest<AddLandmarkDataHandler>;
 
diff --git a/cartographer_grpc/internal/handlers/add_odometry_data_handler_test.cc b/cartographer_grpc/internal/handlers/add_odometry_data_handler_test.cc
index 25c07c2..dd30b74 100644
--- a/cartographer_grpc/internal/handlers/add_odometry_data_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/add_odometry_data_handler_test.cc
@@ -30,7 +30,7 @@ using ::testing::Eq;
 using ::testing::Pointee;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
   sensor_metadata {
     trajectory_id: 1
     sensor_id: "sensor_id"
@@ -45,7 +45,7 @@ const std::string kMessage = R"PROTO(
         w: 6 x: 7 y: 8 z: 9
       }
     }
-  })PROTO";
+  })";
 
 using AddOdometryDataHandlerTest = testing::HandlerTest<AddOdometryDataHandler>;
 
diff --git a/cartographer_grpc/internal/handlers/add_rangefinder_data_handler_test.cc b/cartographer_grpc/internal/handlers/add_rangefinder_data_handler_test.cc
index 4b6983e..3c70355 100644
--- a/cartographer_grpc/internal/handlers/add_rangefinder_data_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/add_rangefinder_data_handler_test.cc
@@ -30,7 +30,7 @@ using ::testing::Eq;
 using ::testing::Pointee;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
   sensor_metadata {
     trajectory_id: 1
     sensor_id: "sensor_id"
@@ -43,7 +43,7 @@ const std::string kMessage = R"PROTO(
     point_data {
       x: 6.f y: 7.f z: 8.f t: 9.f
     }
-  })PROTO";
+  })";
 
 using AddRangefinderDataHandlerTest =
     testing::HandlerTest<AddRangefinderDataHandler>;
diff --git a/cartographer_grpc/internal/handlers/add_trajectory_handler_test.cc b/cartographer_grpc/internal/handlers/add_trajectory_handler_test.cc
index 3e51d82..cfed50a 100644
--- a/cartographer_grpc/internal/handlers/add_trajectory_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/add_trajectory_handler_test.cc
@@ -35,7 +35,7 @@ using ::testing::ReturnRef;
 using ::testing::Test;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
     expected_sensor_ids {
       id: "range_sensor"
       type: RANGE
@@ -63,7 +63,7 @@ const std::string kMessage = R"PROTO(
         timestamp: 9
       }
     }
-  )PROTO";
+  )";
 
 class AddTrajectoryHandlerTest
     : public testing::HandlerTest<AddTrajectoryHandler> {
diff --git a/cartographer_grpc/internal/handlers/get_landmark_poses_handler_test.cc b/cartographer_grpc/internal/handlers/get_landmark_poses_handler_test.cc
index a74c495..144e315 100644
--- a/cartographer_grpc/internal/handlers/get_landmark_poses_handler_test.cc
+++ b/cartographer_grpc/internal/handlers/get_landmark_poses_handler_test.cc
@@ -31,7 +31,7 @@ using ::testing::Eq;
 using ::testing::Pointee;
 using ::testing::Truly;
 
-const std::string kMessage = R"PROTO(
+const std::string kMessage = R"(
   landmark_poses {
     landmark_id: "landmark_1"
     global_pose {
@@ -54,7 +54,7 @@ const std::string kMessage = R"PROTO(
       }
     }
   }
-)PROTO";
+)";
 
 using GetLandmarkPosesHandlerTest =
     testing::HandlerTest<GetLandmarkPosesHandler>;