diff --git a/client.go b/client.go
index 3936464..0fe5c42 100644
--- a/client.go
+++ b/client.go
@@ -106,7 +106,7 @@ func (c *Client) partChannel(channelName, reason string) {
 		return
 	}
 
-	if _, inChannel := channel.clientMap[strings.ToLower(c.nick)]; inChannel == false {
+	if _, inChannel := channel.clientMap[c.key]; inChannel == false {
 		//Client isn't in this channel, do nothing
 		return
 	}
@@ -117,8 +117,8 @@ func (c *Client) partChannel(channelName, reason string) {
 	}
 
 	delete(c.channelMap, channelKey)
-	delete(channel.modeMap, strings.ToLower(c.nick))
-	delete(channel.clientMap, strings.ToLower(c.nick))
+	delete(channel.modeMap, c.key)
+	delete(channel.clientMap, c.key)
 
 	if len(channel.clientMap) == 0 {
 		delete(c.server.channelMap, channelKey)
@@ -227,7 +227,7 @@ func (c *Client) clientThread() {
 			c.partChannel(channelName, "Disconnecting")
 		}
 
-		delete(c.server.clientMap, strings.ToLower(c.nick))
+		delete(c.server.clientMap, c.key)
 
 		c.connection.Close()
 	}()
diff --git a/server.go b/server.go
index 4147cef..23a1c5c 100644
--- a/server.go
+++ b/server.go
@@ -184,14 +184,14 @@ func (s *Server) handleCommand(client *Client, command string, args []string) {
 
 		if chanExists {
 			if channel.mode.noExternal {
-				if _, inChannel := channel.clientMap[strings.ToLower(client.nick)]; !inChannel {
+				if _, inChannel := channel.clientMap[client.key]; !inChannel {
 					//Not in channel, not allowed to send
 					client.reply(errCannotSend, args[0])
 					return
 				}
 			}
 			if channel.mode.moderated {
-				clientMode := channel.modeMap[strings.ToLower(client.nick)]
+				clientMode := channel.modeMap[client.key]
 				if !clientMode.operator && !clientMode.voice {
 					//It's moderated and we're not +v or +o, do nothing
 					client.reply(errCannotSend, args[0])
@@ -239,7 +239,7 @@ func (s *Server) handleCommand(client *Client, command string, args []string) {
 			return
 		}
 
-		clientMode := channel.modeMap[strings.ToLower(client.nick)]
+		clientMode := channel.modeMap[client.key]
 		if channel.mode.topicLocked && !clientMode.operator {
 			client.reply(errNoPriv)
 			return
@@ -271,7 +271,7 @@ func (s *Server) handleCommand(client *Client, command string, args []string) {
 
 			for channelName, channel := range s.channelMap {
 				if channel.mode.secret {
-					if _, inChannel := channel.clientMap[strings.ToLower(client.nick)]; !inChannel {
+					if _, inChannel := channel.clientMap[client.key]; !inChannel {
 						//Not in the channel, skip
 						continue
 					}
@@ -419,7 +419,7 @@ func (s *Server) handleCommand(client *Client, command string, args []string) {
 			return
 		}
 
-		if cm, ok := channel.modeMap[strings.ToLower(client.nick)]; !ok || !cm.operator {
+		if cm, ok := channel.modeMap[client.key]; !ok || !cm.operator {
 			//Not a channel operator.
 
 			//If they're not an irc operator either, they'll fail