diff --git a/src/rosbags/convert/converter.py b/src/rosbags/convert/converter.py
index 65c3a5f9..03af6168 100644
--- a/src/rosbags/convert/converter.py
+++ b/src/rosbags/convert/converter.py
@@ -106,13 +106,13 @@ def convert_1to2(src: Path, dst: Path) -> None:
             candidate = upgrade_connection(rconn)
             existing = next((x for x in writer.connections.values() if x == candidate), None)
             wconn = existing if existing else writer.add_connection(**asdict(candidate))
-            connmap[rconn.cid] = wconn
+            connmap[rconn.id] = wconn
             typs.update(get_types_from_msg(rconn.msgdef, rconn.msgtype))
         register_types(typs)
 
         for rconn, timestamp, data in reader.messages():
             data = ros1_to_cdr(data, rconn.msgtype)
-            writer.write(connmap[rconn.cid], timestamp, data)
+            writer.write(connmap[rconn.id], timestamp, data)
 
 
 def convert_2to1(src: Path, dst: Path) -> None:
diff --git a/src/rosbags/rosbag1/reader.py b/src/rosbags/rosbag1/reader.py
index c7733c66..8798c529 100644
--- a/src/rosbags/rosbag1/reader.py
+++ b/src/rosbags/rosbag1/reader.py
@@ -53,7 +53,7 @@ class RecordType(IntEnum):
 class Connection(NamedTuple):
     """Connection information."""
 
-    cid: int
+    id: int
     topic: str
     msgtype: str
     msgdef: str
@@ -436,7 +436,7 @@ class Reader:
                 count = reduce(
                     lambda x, y: x + y,
                     (
-                        y.connection_counts.get(x.cid, 0)
+                        y.connection_counts.get(x.id, 0)
                         for x in connections
                         for y in self.chunk_infos
                     ),
@@ -607,7 +607,7 @@ class Reader:
         if not connections:
             connections = self.connections.values()
 
-        indexes = [self.indexes[x.cid] for x in connections]
+        indexes = [self.indexes[x.id] for x in connections]
         for entry in heapq.merge(*indexes):
             if start and entry.time < start:
                 continue
diff --git a/src/rosbags/rosbag1/writer.py b/src/rosbags/rosbag1/writer.py
index 2d5076ea..8063757f 100644
--- a/src/rosbags/rosbag1/writer.py
+++ b/src/rosbags/rosbag1/writer.py
@@ -261,7 +261,7 @@ class Writer:
         bio = self.chunks[-1].data
         self.write_connection(connection, bio)
 
-        self.connections[connection.cid] = connection
+        self.connections[connection.id] = connection
         return connection
 
     def write(self, connection: Connection, timestamp: int, data: bytes) -> None:
@@ -283,7 +283,7 @@ class Writer:
             raise WriterError(f'There is no connection {connection!r}.') from None
 
         chunk = self.chunks[-1]
-        chunk.connections[connection.cid].append((timestamp, chunk.data.tell()))
+        chunk.connections[connection.id].append((timestamp, chunk.data.tell()))
 
         if timestamp < chunk.start:
             chunk.start = timestamp
@@ -292,7 +292,7 @@ class Writer:
             chunk.end = timestamp
 
         header = Header()
-        header.set_uint32('conn', connection.cid)
+        header.set_uint32('conn', connection.id)
         header.set_time('time', timestamp)
 
         header.write(chunk.data, RecordType.MSGDATA)
@@ -305,7 +305,7 @@ class Writer:
     def write_connection(connection: Connection, bio: BinaryIO) -> None:
         """Write connection record."""
         header = Header()
-        header.set_uint32('conn', connection.cid)
+        header.set_uint32('conn', connection.id)
         header.set_string('topic', connection.topic)
         header.write(bio, RecordType.CONNECTION)
 
diff --git a/tests/test_writer1.py b/tests/test_writer1.py
index 28ba6cee..dd188525 100644
--- a/tests/test_writer1.py
+++ b/tests/test_writer1.py
@@ -49,7 +49,7 @@ def test_add_connection(tmp_path: Path) -> None:
 
     with Writer(path) as writer:
         res = writer.add_connection('/foo', 'test_msgs/msg/Test', 'MESSAGE_DEFINITION', 'HASH')
-        assert res.cid == 0
+        assert res.id == 0
     data = path.read_bytes()
     assert data.count(b'MESSAGE_DEFINITION') == 2
     assert data.count(b'HASH') == 2
@@ -57,7 +57,7 @@ def test_add_connection(tmp_path: Path) -> None:
 
     with Writer(path) as writer:
         res = writer.add_connection('/foo', 'std_msgs/msg/Int8')
-        assert res.cid == 0
+        assert res.id == 0
     data = path.read_bytes()
     assert data.count(b'int8 data') == 2
     assert data.count(b'27ffa0c9c4b8fb8492252bcad9e5c57b') == 2
@@ -85,7 +85,7 @@ def test_add_connection(tmp_path: Path) -> None:
             'HASH',
             latching=1,
         )
-        assert (res1.cid, res2.cid, res3.cid) == (0, 1, 2)
+        assert (res1.id, res2.id, res3.id) == (0, 1, 2)
 
 
 def test_write_errors(tmp_path: Path) -> None: