diff --git a/src/common/lib/transport/messagequeue.ts b/src/common/lib/transport/messagequeue.ts
index a335a585b..f5d775e0a 100644
--- a/src/common/lib/transport/messagequeue.ts
+++ b/src/common/lib/transport/messagequeue.ts
@@ -39,34 +39,49 @@ class MessageQueue extends EventEmitter {
     this.messages.unshift.apply(this.messages, messages);
   }
 
-  completeMessages(serial: number, count: number, err?: ErrorInfo | null): void {
+  /**
+   * For all messages targeted by the selector, calls their callback and removes them from the queue.
+   *
+   * @param selector - Describes which messages to target. 'all' means all messages in the queue (regardless of whether they have had a `msgSerial` assigned); `serial` / `count` targets a range of messages described by an `ACK` or `NACK` received from Ably (this assumes that all the messages in the queue have had a `msgSerial` assigned).
+   */
+  completeMessages(selector: 'all' | { serial: number; count: number }, err?: ErrorInfo | null): void {
     Logger.logAction(
       this.logger,
       Logger.LOG_MICRO,
       'MessageQueue.completeMessages()',
-      'serial = ' + serial + '; count = ' + count,
+      selector == 'all' ? '(all)' : 'serial = ' + selector.serial + '; count = ' + selector.count,
     );
     err = err || null;
     const messages = this.messages;
     if (messages.length === 0) {
       throw new Error('MessageQueue.completeMessages(): completeMessages called on any empty MessageQueue');
     }
-    const first = messages[0];
-    if (first) {
-      const startSerial = first.message.msgSerial as number;
-      const endSerial = serial + count; /* the serial of the first message that is *not* the subject of this call */
-      if (endSerial > startSerial) {
-        const completeMessages = messages.splice(0, endSerial - startSerial);
-        for (const message of completeMessages) {
-          (message.callback as Function)(err);
+
+    let completeMessages: PendingMessage[] = [];
+
+    if (selector === 'all') {
+      completeMessages = messages.splice(0);
+    } else {
+      const first = messages[0];
+      if (first) {
+        const startSerial = first.message.msgSerial as number;
+        const endSerial =
+          selector.serial + selector.count; /* the serial of the first message that is *not* the subject of this call */
+        if (endSerial > startSerial) {
+          completeMessages = messages.splice(0, endSerial - startSerial);
         }
       }
-      if (messages.length == 0) this.emit('idle');
     }
+
+    for (const message of completeMessages) {
+      (message.callback as Function)(err);
+    }
+
+    if (messages.length == 0) this.emit('idle');
   }
 
   completeAllMessages(err: ErrorInfo): void {
-    this.completeMessages(0, Number.MAX_SAFE_INTEGER || Number.MAX_VALUE, err);
+    this.completeMessages('all', err);
   }
 
   resetSendAttempted(): void {
diff --git a/src/common/lib/transport/protocol.ts b/src/common/lib/transport/protocol.ts
index e3f1590e1..a9eb3eb7d 100644
--- a/src/common/lib/transport/protocol.ts
+++ b/src/common/lib/transport/protocol.ts
@@ -45,7 +45,7 @@ class Protocol extends EventEmitter {
 
   onAck(serial: number, count: number): void {
     Logger.logAction(this.logger, Logger.LOG_MICRO, 'Protocol.onAck()', 'serial = ' + serial + '; count = ' + count);
-    this.messageQueue.completeMessages(serial, count);
+    this.messageQueue.completeMessages({ serial, count });
   }
 
   onNack(serial: number, count: number, err: ErrorInfo): void {
@@ -58,7 +58,7 @@ class Protocol extends EventEmitter {
     if (!err) {
       err = new ErrorInfo('Unable to send message; channel not responding', 50001, 500);
     }
-    this.messageQueue.completeMessages(serial, count, err);
+    this.messageQueue.completeMessages({ serial, count }, err);
   }
 
   onceIdle(listener: ErrCallback): void {
diff --git a/test/common/modules/private_api_recorder.js b/test/common/modules/private_api_recorder.js
index 338fe3ffb..fc01599b7 100644
--- a/test/common/modules/private_api_recorder.js
+++ b/test/common/modules/private_api_recorder.js
@@ -103,6 +103,7 @@ define(['test/support/output_directory_paths'], function (outputDirectoryPaths)
     'read.connectionManager.connectionId',
     'read.connectionManager.connectionStateTtl',
     'read.connectionManager.domains',
+    'read.connectionManager.queuedMessages',
     'read.connectionManager.msgSerial',
     'read.connectionManager.options',
     'read.connectionManager.options.timeouts.httpMaxRetryDuration',
diff --git a/test/realtime/failure.test.js b/test/realtime/failure.test.js
index 789c1d347..84dc8a646 100644
--- a/test/realtime/failure.test.js
+++ b/test/realtime/failure.test.js
@@ -479,16 +479,16 @@ define(['ably', 'shared_helper', 'async', 'chai'], function (Ably, Helper, async
     });
 
     /* RTN7c
-     * Publish a message, then before it receives an ack, disconnect the
+     * Publish a message whilst CONNECTED, then before it receives an ack, disconnect the
      * transport, and let the connection go into some terminal failure state.
      * Check that the publish callback is called with an error.
      */
-    function nack_on_connection_failure(failureFn, expectedRealtimeState, expectedNackCode) {
+    function nack_of_sent_message_on_connection_failure(failureFn, expectedRealtimeState, expectedNackCode) {
       return function (done) {
         /* Use one transport because stubbing out transport#onProtocolMesage */
-        var helper = this.test.helper.withParameterisedTestTitle('nack_on_connection_failure'),
+        var helper = this.test.helper.withParameterisedTestTitle('nack_of_sent_message_on_connection_failure'),
           realtime = helper.AblyRealtime({ transports: [helper.bestTransport] }),
-          channel = realtime.channels.get('nack_on_connection_failure');
+          channel = realtime.channels.get('nack_of_sent_message_on_connection_failure');
 
         async.series(
           [
@@ -539,10 +539,10 @@ define(['ably', 'shared_helper', 'async', 'chai'], function (Ably, Helper, async
       };
     }
 
-    /** @specpartial RTN7c - test for SUSPENDED */
+    /** @specpartial RTN7c - test for SUSPENDED in the case where the message has been sent on the transport */
     it(
-      'nack_on_connection_suspended',
-      nack_on_connection_failure(
+      'nack_of_sent_message_on_connection_suspended',
+      nack_of_sent_message_on_connection_failure(
         function (realtime, helper) {
           helper.becomeSuspended(realtime);
         },
@@ -551,10 +551,10 @@ define(['ably', 'shared_helper', 'async', 'chai'], function (Ably, Helper, async
       ),
     );
 
-    /** @specpartial RTN7c - test for FAILED */
+    /** @specpartial RTN7c - test for FAILED in the case where the message has been sent on the transport */
     it(
-      'nack_on_connection_failed',
-      nack_on_connection_failure(
+      'nack_of_sent_message_on_connection_failed',
+      nack_of_sent_message_on_connection_failure(
         function (realtime, helper) {
           helper.recordPrivateApi('read.connectionManager.activeProtocol.transport');
           helper.recordPrivateApi('call.transport.onProtocolMessage');
@@ -568,10 +568,113 @@ define(['ably', 'shared_helper', 'async', 'chai'], function (Ably, Helper, async
       ),
     );
 
-    /** @specpartial RTN7c - test for CLOSED */
+    /** @specpartial RTN7c - test for CLOSED in the case where the message has been sent on the transport */
     it(
-      'nack_on_connection_closed',
-      nack_on_connection_failure(
+      'nack_of_sent_message_on_connection_closed',
+      nack_of_sent_message_on_connection_failure(
+        function (realtime) {
+          realtime.close();
+        },
+        'closed',
+        80017,
+      ),
+    );
+
+    /* RTN7c
+     * Publish a message whilst not CONNECTED, then whilst the message is still
+     * queued let the connection go into some terminal failure state. Check
+     * that the publish callback is called with an error.
+     */
+    function nack_of_queued_message_on_connection_failure(failureFn, expectedRealtimeState, expectedNackCode) {
+      return function (done) {
+        /* Use one transport because stubbing out transport#onProtocolMesage */
+        var helper = this.test.helper.withParameterisedTestTitle('nack_of_queued_message_on_connection_failure'),
+          realtime = helper.AblyRealtime({ transports: [helper.bestTransport] }),
+          channel = realtime.channels.get('nack_of_queued_message_on_connection_failure');
+
+        // Drop inbound CONNECTED so that we don't become CONNECTED
+        helper.recordPrivateApi('listen.connectionManager.transport.pending');
+        realtime.connection.connectionManager.on('transport.pending', function (transport) {
+          var originalOnProtocolMessage = transport.onProtocolMessage;
+          helper.recordPrivateApi('replace.transport.onProtocolMessage');
+          transport.onProtocolMessage = function (message) {
+            if (message.action !== 4) {
+              helper.recordPrivateApi('call.transport.onProtocolMessage');
+              originalOnProtocolMessage.call(this, message);
+            }
+          };
+        });
+
+        async.series(
+          [
+            function (cb) {
+              Helper.whenPromiseSettles(channel.publish('foo', 'bar'), function (err) {
+                try {
+                  expect(err, 'Publish failed as expected').to.be.ok;
+                  expect(realtime.connection.state).to.equal(
+                    expectedRealtimeState,
+                    'check realtime state is ' + expectedRealtimeState,
+                  );
+                  expect(err.code).to.equal(expectedNackCode, 'Check error code was ' + expectedNackCode);
+                  cb();
+                } catch (err) {
+                  cb(err);
+                }
+              });
+              // We wait for the `publish()`-ed message to appear in the message queue before enacting the connection state change (queueing is preceded by asynchronous encoding). AFAIK there isn't an event-driven internal API for this so we'll just poll.
+              (async () => {
+                helper.recordPrivateApi('call.Platform.nextTick');
+                helper.recordPrivateApi('read.connectionManager.queuedMessages');
+                while (true) {
+                  await new Promise((res) => Ably.Realtime.Platform.Config.nextTick(res));
+                  if (realtime.connection.connectionManager.queuedMessages.count() > 0) {
+                    failureFn(realtime, helper.withParameterisedTestTitle(null));
+                    break;
+                  }
+                }
+              })();
+            },
+          ],
+          function (err) {
+            helper.closeAndFinish(done, realtime, err);
+          },
+        );
+      };
+    }
+
+    /** @specpartial RTN7c - test for SUSPENDED in the case where the message has not yet been sent on the transport */
+    it(
+      'nack_of_queued_message_on_connection_suspended',
+      nack_of_queued_message_on_connection_failure(
+        function (realtime, helper) {
+          helper.recordPrivateApi('call.connectionManager.notifyState');
+          realtime.connection.connectionManager.notifyState({ state: 'suspended' });
+        },
+        'suspended',
+        80002,
+      ),
+    );
+
+    /** @specpartial RTN7c - test for FAILED in the case where the message has not yet been sent on the transport */
+    it(
+      'nack_of_queued_message_on_connection_failed',
+      nack_of_queued_message_on_connection_failure(
+        function (realtime, helper) {
+          helper.recordPrivateApi('call.connectionManager.notifyState');
+          realtime.connection.connectionManager.notifyState({
+            state: 'failed',
+            error: { statusCode: 401, code: 40100, message: 'connection failed because reasons' },
+          });
+        },
+        'failed',
+        40100,
+      ),
+    );
+
+    /** @specpartial RTN7c - test for CLOSED in the case where the message has not yet been sent on the transport */
+    it(
+      'nack_of_queued_message_on_connection_closed',
+      nack_of_queued_message_on_connection_failure(
         function (realtime) {
           realtime.close();
         },