diff --git a/lib/ably/realtime/channel.rb b/lib/ably/realtime/channel.rb
index 162b153b..af1772c0 100644
--- a/lib/ably/realtime/channel.rb
+++ b/lib/ably/realtime/channel.rb
@@ -364,8 +364,8 @@ def __incoming_msgbus__
       # @return [Ably::Models::ChannelOptions]
       def set_options(channel_options)
         @options = Ably::Models::ChannelOptions(channel_options)
-
-        manager.request_reattach if need_reattach?
+        # RTL4i
+        manager.request_reattach if (need_reattach? and connection.state?(:connected))
       end
       alias options= set_options
 
diff --git a/lib/ably/realtime/channel/channel_manager.rb b/lib/ably/realtime/channel/channel_manager.rb
index 9c0fdc02..90f00b9e 100644
--- a/lib/ably/realtime/channel/channel_manager.rb
+++ b/lib/ably/realtime/channel/channel_manager.rb
@@ -18,7 +18,7 @@ def initialize(channel, connection)
       def attach
         if can_transition_to?(:attached)
           connect_if_connection_initialized
-          send_attach_protocol_message
+          send_attach_protocol_message if connection.state?(:connected) # RTL4i
         end
       end
 
@@ -49,14 +49,12 @@ def log_channel_error(error)
       end
 
       # Request channel to be reattached by sending an attach protocol message
-      # @param [Hash] options
-      # @option options [Ably::Models::ErrorInfo]  :reason
-      def request_reattach(options = {})
-        reason = options[:reason]
-        send_attach_protocol_message
-        logger.debug { "Explicit channel reattach request sent to Ably due to #{reason}" }
+      # @param [Ably::Models::ErrorInfo] reason
+      def request_reattach(reason = nil)
         channel.set_channel_error_reason(reason) if reason
         channel.transition_state_machine! :attaching, reason: reason unless channel.attaching?
+        send_attach_protocol_message
+        logger.debug { "Explicit channel reattach request sent to Ably due to #{reason}" }
       end
 
       def duplicate_attached_received(protocol_message)
@@ -169,6 +167,12 @@ def start_attach_from_suspended_timer
         end
       end
 
+      # RTL13c
+      def notify_state_change
+        @pending_state_change_timer.cancel if @pending_state_change_timer
+        @pending_state_change_timer = nil
+      end
+
       private
       attr_reader :pending_state_change_timer
 
@@ -209,48 +213,55 @@ def send_attach_protocol_message
         end
 
         message_options[:channelSerial] = channel.properties.channel_serial # RTL4c1
-        send_state_change_protocol_message Ably::Models::ProtocolMessage::ACTION.Attach, :suspended, message_options
-      end
 
-      def send_detach_protocol_message(previous_state)
-        send_state_change_protocol_message Ably::Models::ProtocolMessage::ACTION.Detach, previous_state # return to previous state if failed
-      end
-
-      def send_state_change_protocol_message(new_state, state_if_failed, message_options = {})
         state_at_time_of_request = channel.state
+        attach_action = Ably::Models::ProtocolMessage::ACTION.Attach
+        # RTL4f
         @pending_state_change_timer = EventMachine::Timer.new(realtime_request_timeout) do
           if channel.state == state_at_time_of_request
-            error = Ably::Models::ErrorInfo.new(code: Ably::Exceptions::Codes::CHANNEL_OPERATION_FAILED_NO_RESPONSE_FROM_SERVER, message: "Channel #{new_state} operation failed (timed out)")
-            channel.transition_state_machine state_if_failed, reason: error
+            error = Ably::Models::ErrorInfo.new(code: Ably::Exceptions::Codes::CHANNEL_OPERATION_FAILED_NO_RESPONSE_FROM_SERVER, message: "Channel #{attach_action} operation failed (timed out)")
+            channel.transition_state_machine :suspended, reason: error # return to suspended state if failed
           end
         end
+        # Shouldn't queue attach message as per RTL4i, so message is added top of the queue
+        # to be sent immediately while processing next message
+        connection.send_protocol_message_immediately(
+          action:  attach_action.to_i,
+          channel: channel.name,
+          **message_options.to_h
+        )
+      end
 
-        channel.once_state_changed do
-          @pending_state_change_timer.cancel if @pending_state_change_timer
-          @pending_state_change_timer = nil
+      def send_detach_protocol_message(previous_state)
+        state_at_time_of_request = channel.state
+        detach_action = Ably::Models::ProtocolMessage::ACTION.Detach
+
+        @pending_state_change_timer = EventMachine::Timer.new(realtime_request_timeout) do
+          if channel.state == state_at_time_of_request
+            error = Ably::Models::ErrorInfo.new(code: Ably::Exceptions::Codes::CHANNEL_OPERATION_FAILED_NO_RESPONSE_FROM_SERVER, message: "Channel #{detach_action} operation failed (timed out)")
+            channel.transition_state_machine previous_state, reason: error # return to previous state if failed
+          end
         end
 
-        resend_if_disconnected_and_connected = lambda do
+        on_disconnected_and_connected = lambda do
           connection.unsafe_once(:disconnected) do
-            next unless pending_state_change_timer
             connection.unsafe_once(:connected) do
-              next unless pending_state_change_timer
-              connection.send_protocol_message(
-                action:  new_state.to_i,
-                channel: channel.name,
-                **message_options.to_h
-              )
-              resend_if_disconnected_and_connected.call
-            end
+              yield if pending_state_change_timer
+            end if pending_state_change_timer
           end
         end
-        resend_if_disconnected_and_connected.call
 
-        connection.send_protocol_message(
-          action:  new_state.to_i,
-          channel: channel.name,
-          **message_options.to_h
-        )
+        send_detach_message = lambda do
+          on_disconnected_and_connected.call do
+            send_detach_message.call
+          end
+          connection.send_protocol_message(
+            action:  detach_action.to_i,
+            channel: channel.name
+          )
+        end
+
+        send_detach_message.call
       end
 
       def logger
diff --git a/lib/ably/realtime/channel/channel_state_machine.rb b/lib/ably/realtime/channel/channel_state_machine.rb
index a346fec2..e3cedd18 100644
--- a/lib/ably/realtime/channel/channel_state_machine.rb
+++ b/lib/ably/realtime/channel/channel_state_machine.rb
@@ -29,6 +29,7 @@ class ChannelStateMachine
       transition :from => :failed,       :to => [:attaching, :initialized]
 
       after_transition do |channel, transition|
+        channel.manager.notify_state_change # RTL13c
         channel.synchronize_state_with_statemachine
       end
 
diff --git a/lib/ably/realtime/connection.rb b/lib/ably/realtime/connection.rb
index 008a2116..d4d11289 100644
--- a/lib/ably/realtime/connection.rb
+++ b/lib/ably/realtime/connection.rb
@@ -431,17 +431,28 @@ def logger
       # @api private
       def send_protocol_message(protocol_message)
         add_message_serial_if_ack_required_to(protocol_message) do
-          Ably::Models::ProtocolMessage.new(protocol_message, logger: logger).tap do |message|
-            add_message_to_outgoing_queue message
-            notify_message_dispatcher_of_new_message message
-            logger.debug { "Connection: Prot msg queued =>: #{message.action} #{message}" }
-          end
+          message = Ably::Models::ProtocolMessage.new(protocol_message, logger: logger)
+          add_message_to_outgoing_queue(message)
+          notify_message_dispatcher_of_new_message message
         end
       end
 
+      def send_protocol_message_immediately(protocol_message)
+        message = Ably::Models::ProtocolMessage.new(protocol_message, logger: logger)
+        add_message_to_outgoing_queue(message, true)
+        notify_message_dispatcher_of_new_message message
+      end
+
       # @api private
-      def add_message_to_outgoing_queue(protocol_message)
-        __outgoing_message_queue__ << protocol_message
+      def add_message_to_outgoing_queue(protocol_message, send_immediately = false)
+        if send_immediately
+          # Adding msg at the top of the queue to get processed immediately while connection is CONNECTED
+          __outgoing_message_queue__.prepend(protocol_message)
+          logger.debug { "Connection: protocol msg pushed at the top =>: #{message.action} #{message}" }
+        else
+          __outgoing_message_queue__ << protocol_message
+          logger.debug { "Connection: protocol msg queued =>: #{message.action} #{message}" }
+        end
       end
 
       # @api private
diff --git a/lib/ably/realtime/connection/connection_manager.rb b/lib/ably/realtime/connection/connection_manager.rb
index cd62f637..5c2d2ab8 100644
--- a/lib/ably/realtime/connection/connection_manager.rb
+++ b/lib/ably/realtime/connection/connection_manager.rb
@@ -582,7 +582,7 @@ def force_reattach_on_channels(error)
         channels.select do |channel|
           channel.attached? || channel.attaching? || channel.suspended?
         end.each do |channel|
-          channel.manager.request_reattach reason: error
+          channel.manager.request_reattach error
         end
       end
 
diff --git a/spec/acceptance/realtime/channel_spec.rb b/spec/acceptance/realtime/channel_spec.rb
index d2c4250e..5c7bc06e 100644
--- a/spec/acceptance/realtime/channel_spec.rb
+++ b/spec/acceptance/realtime/channel_spec.rb
@@ -430,9 +430,35 @@ def disconnect_transport
       end
 
       context 'with connection state' do
+
+        sent_attach_messages = []
+        received_attached_messages = []
+        before(:each) do
+          sent_attach_messages = []
+          received_attached_messages = []
+          client.connection.__outgoing_protocol_msgbus__.subscribe do |message|
+            if message.action == :attach
+              sent_attach_messages << message
+            end
+          end
+          client.connection.__incoming_protocol_msgbus__.subscribe do |message|
+            if message.action == :attached
+              received_attached_messages << message
+            end
+          end
+        end
+
+        # Should send/receive attach/attached message only once
+        # No duplicates should be sent or received
+        let(:check_for_attach_messages) do
+          expect(sent_attach_messages.size).to eq(1)
+          expect(received_attached_messages.size).to eq(1)
+        end
+
         it 'is initialized (#RTL4i)' do
           expect(connection).to be_initialized
           channel.attach do
+            check_for_attach_messages
             stop_reactor
           end
         end
@@ -440,6 +466,7 @@ def disconnect_transport
         it 'is connecting (#RTL4i)' do
           connection.once(:connecting) do
             channel.attach do
+              check_for_attach_messages
               stop_reactor
             end
           end
@@ -449,6 +476,7 @@ def disconnect_transport
           connection.once(:connected) do
             connection.once(:disconnected) do
               channel.attach do
+                check_for_attach_messages
                 stop_reactor
               end
             end