diff --git a/infrastructure.go b/infrastructure.go
index 02b57665..8102fc46 100644
--- a/infrastructure.go
+++ b/infrastructure.go
@@ -145,8 +145,8 @@ func (c *Client) NextID() uint64 {
 }
 
 // addRequest associates the passed jsonRequest with the passed id.  This allows
-// the response from the remote server to be unmarshalled to the appropiate type
-// and sent to the specified channel when it is received.
+// the response from the remote server to be unmarshalled to the appropriate
+// type and sent to the specified channel when it is received.
 //
 // If the client has already begun shutting down, ErrClientShutdown is returned
 // and the request is not added.
@@ -196,11 +196,8 @@ func (c *Client) removeRequest(id uint64) *jsonRequest {
 // removeAllRequests removes all the jsonRequests which contain the response
 // channels for outstanding requests.
 //
-// This function is safe for concurrent access.
+// This function MUST be called with the request lock held.
 func (c *Client) removeAllRequests() {
-	c.requestLock.Lock()
-	defer c.requestLock.Unlock()
-
 	c.requestMap = make(map[uint64]*list.Element)
 	c.requestList.Init()
 }
@@ -416,11 +413,11 @@ cleanup:
 // block until the send channel is full.
 func (c *Client) sendMessage(marshalledJSON []byte) {
 	// Don't send the message if disconnected.
-	if c.Disconnected() {
+	select {
+	case c.sendChan <- marshalledJSON:
+	case <-c.disconnect:
 		return
 	}
-
-	c.sendChan <- marshalledJSON
 }
 
 // reregisterNtfns creates and sends commands needed to re-establish the current
@@ -824,14 +821,14 @@ func (c *Client) Disconnected() bool {
 	return c.disconnected
 }
 
-// Disconnect disconnects the current websocket associated with the client.  The
-// connection will automatically be re-established unless the client was
-// created with the DisableAutoReconnect flag.
+// doDisconnect disconnects the websocket associated with the client if it
+// hasn't already been disconnected.  It will return false if the disconnect is
+// not needed or the client is running in HTTP POST mode.
 //
-// This function has no effect when the client is running in HTTP POST mode.
-func (c *Client) Disconnect() {
+// This function is safe for concurrent access.
+func (c *Client) doDisconnect() bool {
 	if c.config.HttpPostMode {
-		return
+		return false
 	}
 
 	c.mtx.Lock()
@@ -839,18 +836,51 @@ func (c *Client) Disconnect() {
 
 	// Nothing to do if already disconnected.
 	if c.disconnected {
-		return
+		return false
 	}
 
 	log.Tracef("Disconnecting RPC client %s", c.config.Host)
 	close(c.disconnect)
 	c.wsConn.Close()
 	c.disconnected = true
+	return true
+}
+
+// doShutdown closes the shutdown channel and logs the shutdown unless shutdown
+// is already in progress.  It will return false if the shutdown is not needed.
+//
+// This function is safe for concurrent access.
+func (c *Client) doShutdown() bool {
+	// Ignore the shutdown request if the client is already in the process
+	// of shutting down or already shutdown.
+	select {
+	case <-c.shutdown:
+		return false
+	default:
+	}
+
+	log.Tracef("Shutting down RPC client %s", c.config.Host)
+	close(c.shutdown)
+	return true
+}
+
+// Disconnect disconnects the current websocket associated with the client.  The
+// connection will automatically be re-established unless the client was
+// created with the DisableAutoReconnect flag.
+//
+// This function has no effect when the client is running in HTTP POST mode.
+func (c *Client) Disconnect() {
+	// Nothing to do if already disconnected or running in HTTP POST mode.
+	if !c.doDisconnect() {
+		return
+	}
+
+	c.requestLock.Lock()
+	defer c.requestLock.Unlock()
 
 	// When operating without auto reconnect, send errors to any pending
 	// requests and shutdown the client.
 	if c.config.DisableAutoReconnect {
-		c.requestLock.Lock()
 		for e := c.requestList.Front(); e != nil; e = e.Next() {
 			req := e.Value.(*jsonRequest)
 			req.responseChan <- &response{
@@ -858,9 +888,8 @@ func (c *Client) Disconnect() {
 				err:    ErrClientDisconnect,
 			}
 		}
-		c.requestLock.Unlock()
 		c.removeAllRequests()
-		c.Shutdown()
+		c.doShutdown()
 	}
 }
 
@@ -868,19 +897,18 @@ func (c *Client) Disconnect() {
 // with the client and, when automatic reconnect is enabled, preventing future
 // attempts to reconnect.  It also stops all goroutines.
 func (c *Client) Shutdown() {
+	// Do the shutdown under the request lock to prevent clients from
+	// adding new requests while the client shutdown process is initiated.
+	c.requestLock.Lock()
+	defer c.requestLock.Unlock()
+
 	// Ignore the shutdown request if the client is already in the process
 	// of shutting down or already shutdown.
-	select {
-	case <-c.shutdown:
+	if !c.doShutdown() {
 		return
-	default:
 	}
 
-	log.Tracef("Shutting down RPC client %s", c.config.Host)
-	close(c.shutdown)
-
 	// Send the ErrClientShutdown error to any pending requests.
-	c.requestLock.Lock()
 	for e := c.requestList.Front(); e != nil; e = e.Next() {
 		req := e.Value.(*jsonRequest)
 		req.responseChan <- &response{
@@ -888,10 +916,10 @@ func (c *Client) Shutdown() {
 			err:    ErrClientShutdown,
 		}
 	}
-	c.requestLock.Unlock()
 	c.removeAllRequests()
 
-	c.Disconnect()
+	// Disconnect the client if needed.
+	c.doDisconnect()
 }
 
 // Start begins processing input and output messages.