diff --git a/amqp/connection.py b/amqp/connection.py
index 3e9097fd..1dd52c1a 100644
--- a/amqp/connection.py
+++ b/amqp/connection.py
@@ -484,6 +484,7 @@ def collect(self):
     def _get_free_channel_id(self):
         for channel_id in range(1, self.channel_max):
             if channel_id not in self._used_channel_ids:
+                self._used_channel_ids.append(channel_id)
                 return channel_id
 
         raise ResourceError(
diff --git a/t/unit/test_connection.py b/t/unit/test_connection.py
index 03f02585..dfa9a745 100644
--- a/t/unit/test_connection.py
+++ b/t/unit/test_connection.py
@@ -350,6 +350,7 @@ def test_collect_again(self):
 
     def test_get_free_channel_id(self):
         assert self.conn._get_free_channel_id() == 1
+        assert self.conn._get_free_channel_id() == 2
 
     def test_get_free_channel_id__raises_IndexError(self):
         self.conn._used_channel_ids = array('H', range(1, self.conn.channel_max))