diff --git a/server/clustering.go b/server/clustering.go
index 003a7303..9f93bf3e 100644
--- a/server/clustering.go
+++ b/server/clustering.go
@@ -738,6 +738,7 @@ func (r *raftFSM) lookupOrCreateChannel(name string, id uint64) (*channel, error
 			return nil, err
 		}
 		delete(cs.channels, name)
+		delete(s.channels.channelsLC, strings.ToLower(name))
 	}
 	// Channel does exist or has been deleted. Create now with given ID.
 	return cs.createChannelLocked(s, name, id)
diff --git a/server/server.go b/server/server.go
index 46f97f07..66c611f4 100644
--- a/server/server.go
+++ b/server/server.go
@@ -274,16 +274,18 @@ func (state State) String() string {
 
 type channelStore struct {
 	sync.RWMutex
-	channels map[string]*channel
-	store    stores.Store
-	stan     *StanServer
+	channels   map[string]*channel
+	channelsLC map[string]*channel
+	store      stores.Store
+	stan       *StanServer
 }
 
 func newChannelStore(srv *StanServer, s stores.Store) *channelStore {
 	cs := &channelStore{
-		channels: make(map[string]*channel),
-		store:    s,
-		stan:     srv,
+		channels:   make(map[string]*channel),
+		channelsLC: make(map[string]*channel),
+		store:      s,
+		stan:       srv,
 	}
 	return cs
 }
@@ -313,6 +315,13 @@ func (cs *channelStore) createChannel(s *StanServer, name string) (*channel, err
 	return c, err
 }
 
+func (cs *channelStore) checkCase(name string) error {
+	if c := cs.channelsLC[strings.ToLower(name)]; c != nil {
+		return fmt.Errorf("rejecting channel %q because channel %q alreay exists (different cases not allowed)", name, c.name)
+	}
+	return nil
+}
+
 func (cs *channelStore) createChannelLocked(s *StanServer, name string, id uint64) (retChan *channel, retErr error) {
 	defer func() {
 		if retErr != nil {
@@ -329,6 +338,8 @@ func (cs *channelStore) createChannelLocked(s *StanServer, name string, id uint6
 			return nil, ErrChanDelInProgress
 		}
 		return c, nil
+	} else if err := cs.checkCase(name); err != nil {
+		return nil, err
 	}
 	if s.isClustered {
 		if s.isLeader() && id == 0 {
@@ -370,6 +381,7 @@ func (cs *channelStore) create(s *StanServer, name string, sc *stores.Channel) (
 	}
 	c.nextSequence = lastSequence + 1
 	cs.channels[name] = c
+	cs.channelsLC[strings.ToLower(name)] = c
 	cl := cs.store.GetChannelLimits(name)
 	if cl.MaxInactivity > 0 {
 		c.activity = &channelActivity{maxInactivity: cl.MaxInactivity}
@@ -900,6 +912,9 @@ func (s *StanServer) lookupOrCreateChannel(name string) (*channel, error) {
 		}
 		cs.RUnlock()
 		return c, nil
+	} else if err := cs.checkCase(name); err != nil {
+		cs.RUnlock()
+		return nil, err
 	}
 	cs.RUnlock()
 	return cs.createChannel(s, name)
@@ -914,6 +929,9 @@ func (s *StanServer) lookupOrCreateChannelPreventDelete(name string) (*channel,
 			cs.Unlock()
 			return nil, false, ErrChanDelInProgress
 		}
+	} else if err := cs.checkCase(name); err != nil {
+		cs.Unlock()
+		return nil, false, err
 	} else {
 		var err error
 		c, err = cs.createChannelLocked(s, name, 0)
@@ -3127,6 +3145,7 @@ func (s *StanServer) processDeleteChannel(channel string) {
 		return
 	}
 	delete(s.channels.channels, channel)
+	delete(s.channels.channelsLC, strings.ToLower(channel))
 	s.log.Noticef("Channel %q has been deleted", channel)
 }
 
@@ -5287,6 +5306,7 @@ func (s *StanServer) processSubscriptionRequest(m *nats.Msg) {
 		}
 	}
 	if err != nil {
+		s.log.Errorf("Unable to create subscription on %q: %v", sr.Subject, err)
 		s.channels.turnOffPreventDelete(c)
 		s.channels.maybeStartChannelDeleteTimer(sr.Subject, c)
 		s.sendSubscriptionResponseErr(m.Reply, err)
diff --git a/server/server_test.go b/server/server_test.go
index fc9997e5..299f4a04 100644
--- a/server/server_test.go
+++ b/server/server_test.go
@@ -1703,3 +1703,149 @@ func TestInternalSubsLimits(t *testing.T) {
 		})
 	}
 }
+
+func TestChannelNameRejectedIfAlreadyExistsWithDifferentCase(t *testing.T) {
+	for _, tinfo := range []struct {
+		name    string
+		st      string
+		restart bool
+	}{
+		{"memory", stores.TypeMemory, false},
+		{"file", stores.TypeFile, true},
+		{"sql", stores.TypeSQL, true},
+		{"clustered", stores.TypeFile, true},
+	} {
+		t.Run(tinfo.name, func(t *testing.T) {
+			var o *Options
+			if tinfo.st == stores.TypeSQL {
+				if !doSQL {
+					t.SkipNow()
+				}
+			}
+			// Force persistent store to be the tinfo.st for this test.
+			orgps := persistentStoreType
+			persistentStoreType = tinfo.st
+			defer func() { persistentStoreType = orgps }()
+
+			if tinfo.st == stores.TypeSQL || tinfo.st == stores.TypeFile {
+				o = getTestDefaultOptsForPersistentStore()
+			} else if tinfo.st == stores.TypeMemory {
+				o = GetDefaultOptions()
+			}
+
+			cleanupDatastore(t)
+			defer cleanupDatastore(t)
+			cleanupRaftLog(t)
+			defer cleanupRaftLog(t)
+
+			var servers []*StanServer
+			if tinfo.name == "clustered" {
+				ns := natsdTest.RunDefaultServer()
+				defer ns.Shutdown()
+
+				o1 := getTestDefaultOptsForClustering("a", true)
+				servers = append(servers, runServerWithOpts(t, o1, nil))
+				o2 := getTestDefaultOptsForClustering("b", false)
+				servers = append(servers, runServerWithOpts(t, o2, nil))
+				o3 := getTestDefaultOptsForClustering("c", false)
+				servers = append(servers, runServerWithOpts(t, o3, nil))
+			} else {
+				servers = append(servers, runServerWithOpts(t, o, nil))
+			}
+			for _, s := range servers {
+				defer s.Shutdown()
+			}
+
+			sc := NewDefaultConnection(t)
+			defer sc.Close()
+
+			sendOK := func(channel, content string) {
+				t.Helper()
+				if err := sc.Publish(channel, []byte(content)); err != nil {
+					t.Fatalf("Error on send: %v", err)
+				}
+			}
+			sendFail := func(channel, content string) {
+				t.Helper()
+				err := sc.Publish(channel, []byte(content))
+				if err == nil || !strings.Contains(err.Error(), "exists") {
+					t.Fatalf("Expected error that channel already exists, got: %v", err)
+				}
+			}
+			sendOK("Foo", "1")
+			sendOK("Foo", "2")
+			sendOK("Foo", "3")
+			sendOK("Foo", "4")
+			// Change channel name case
+			sendFail("foo", "1")
+			sendFail("foo", "2")
+			// Back to "Foo"
+			sendOK("Foo", "5")
+			sendOK("Foo", "6")
+
+			recvOK := func(channel string) {
+				t.Helper()
+
+				ch := make(chan *stan.Msg, 6)
+				sub, err := sc.Subscribe(channel, func(m *stan.Msg) {
+					ch <- m
+				}, stan.DeliverAllAvailable())
+				if err != nil {
+					t.Fatalf("Error on subscribe: %v", err)
+				}
+				defer sub.Unsubscribe()
+
+				// We want to get all 6 messages
+				for i := 0; i < 6; i++ {
+					select {
+					case m := <-ch:
+						if v, err := strconv.ParseInt(string(m.Data), 10, 64); err != nil || int(v) != i+1 {
+							t.Fatalf("Invalid message %v: %s", i+1, m.Data)
+						}
+					case <-time.After(time.Second):
+						t.Fatalf("Failed receiving message %v", i+1)
+					}
+				}
+			}
+			recvFail := func(channel string) {
+				t.Helper()
+
+				_, err := sc.Subscribe(channel, func(m *stan.Msg) {}, stan.DeliverAllAvailable())
+				if err == nil || !strings.Contains(err.Error(), "exists") {
+					t.Fatalf("Expected error that channel already exists, got %v", err)
+				}
+			}
+			recvOK("Foo")
+			recvFail("foo")
+			recvFail("FoO")
+
+			if !tinfo.restart {
+				return
+			}
+
+			sc.Close()
+
+			for i, s := range servers {
+				s.Shutdown()
+				s.mu.RLock()
+				opts := s.opts
+				s.mu.RUnlock()
+				s = runServerWithOpts(t, opts, nil)
+				defer s.Shutdown()
+				servers[i] = s
+			}
+
+			if tinfo.name == "clustered" {
+				getLeader(t, 10*time.Second, servers...)
+			}
+
+			sc = NewDefaultConnection(t)
+			defer sc.Close()
+
+			// Try to receive again, but change the order...
+			recvFail("foo")
+			recvOK("Foo")
+			recvFail("FoO")
+		})
+	}
+}