diff --git a/README.md b/README.md
index a754b7c..53fe709 100644
--- a/README.md
+++ b/README.md
@@ -1031,14 +1031,14 @@ e.g. `+o-v alice bob`.
 | `441`   | ERR_USERNOTINCHANNEL | The `+o`/`+v` nick is not in the channel                                                                                                                 |
 
 **User modes:** you can query and change only your own; a nick other than your
-own, compared without regard to letter case, gets ERR_USERSDONTMATCH (502). With
-no mode string the server sends RPL_UMODEIS (221) with your modes: `+`, `+o`,
-`+w` or `+ow`. A change is a mode string, `body[0]` over the HTTP API or the
-parameter after the nick on the IRC listener, that starts with `+` or `-`: `w`
-(receive `WALLOPS`) can be set or unset, and `o` (server operator) only unset,
-since only `OPER` sets it. Any other letter, or a string that names no mode,
-gets ERR_UMODEUNKNOWNFLAG (501) and changes nothing. A change that is accepted
-is answered with 221 and the new modes; it is not sent to anyone else.
+own gets ERR_USERSDONTMATCH (502). With no mode string the server sends
+RPL_UMODEIS (221) with your modes: `+`, `+o`, `+w` or `+ow`. A change is a mode
+string, `body[0]` over the HTTP API or the parameter after the nick on the IRC
+listener, that starts with `+` or `-`: `w` (receive `WALLOPS`) can be set or
+unset, and `o` (server operator) only unset, since only `OPER` sets it. Any
+other letter, or a string that names no mode, gets ERR_UMODEUNKNOWNFLAG (501)
+and changes nothing. A change that is accepted is answered with 221 and the new
+modes; it is not sent to anyone else.
 
 ```json
 { "command": "RPL_UMODEIS", "code": 221, "to": "alice", "body": ["+w"] }
@@ -2679,8 +2679,7 @@ IRC_LISTEN_ADDR: ""
   set only over the HTTP API.
 - **User modes**: `+o` (operator, set only via `OPER`), `+w` (receives
   `WALLOPS`). `MODE` for any nick other than your own is rejected with
-  `ERR_USERSDONTMATCH` (502), for both queries and changes. Nick comparison is
-  case-insensitive.
+  `ERR_USERSDONTMATCH` (502), for both queries and changes.
 - **KILL**: an operator's `KILL` broadcasts the victim's `QUIT` to its channel
   peers, deletes its session, and then sends the victim a `KILL` and
   `ERROR :Closing Link` before closing its socket. This applies to victims on
@@ -2701,12 +2700,6 @@ API reaches IRC listener members as an IRC `MODE` line with its value as a
 separate parameter, e.g. `MODE #general +k secretpass` or
 `MODE #general +o bob`.
 
-One gap remains: the IRC listener does not pass on a `PRIVMSG`, `NOTICE`,
-`JOIN`, `PART`, `NICK` or `QUIT` whose sender's nick matches the user's own nick
-ignoring case, so an IRC listener user `alice` never sees these from `Alice`,
-although nicks are case-sensitive. https://git.eeqj.de/sneak/neoirc/issues/128
-tracks it.
-
 ### Docker Usage
 
 To expose the IRC port in Docker (the listener is enabled by default on
diff --git a/internal/handlers/api_test.go b/internal/handlers/api_test.go
index d859b55..e7882f2 100644
--- a/internal/handlers/api_test.go
+++ b/internal/handlers/api_test.go
@@ -669,6 +669,9 @@ func TestCreateSessionDuplicate(t *testing.T) {
 	if resp.StatusCode != http.StatusConflict {
 		t.Fatalf("expected 409, got %d", resp.StatusCode)
 	}
+
+	// Nicks are case-sensitive: Alice is not alice.
+	tserver.createSession("Alice")
 }
 
 // TestEachTestServerHasItsOwnDatabase checks that starting a
diff --git a/internal/handlers/utility.go b/internal/handlers/utility.go
index 30dcb02..50ee0be 100644
--- a/internal/handlers/utility.go
+++ b/internal/handlers/utility.go
@@ -254,8 +254,7 @@ func (hdlr *Handlers) handleWallops(
 
 // handleUserMode handles MODE for a nick: a query when the
 // body is empty, otherwise a change by the mode string in
-// the body. Only the caller's own nick, in any letter case,
-// is allowed.
+// the body. Only the caller's own nick is allowed.
 func (hdlr *Handlers) handleUserMode(
 	writer http.ResponseWriter,
 	request *http.Request,
@@ -263,7 +262,7 @@ func (hdlr *Handlers) handleUserMode(
 	nick, target string,
 	bodyLines func() []string,
 ) {
-	if !strings.EqualFold(target, nick) {
+	if target != nick {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
 			irc.ErrUsersDoNotMatch, nick, nil,
diff --git a/internal/handlers/utility_test.go b/internal/handlers/utility_test.go
index 7afa834..f5dea41 100644
--- a/internal/handlers/utility_test.go
+++ b/internal/handlers/utility_test.go
@@ -290,8 +290,10 @@ func TestUserMode(t *testing.T) {
 		target, modeStr, numeric, modes string
 	}{
 		{nick, "+w", "221", "+w"},
+		{"Alice", "", "502", ""},
+		{"Alice", "-w", "502", ""},
 		{nick, "", "221", "+w"},
-		{strings.ToUpper(nick), "-w", "221", "+"},
+		{nick, "-w", "221", "+"},
 		{nick, "+z", "501", ""},
 		{nick, "+o", "501", ""},
 		{other, "", "502", ""},
diff --git a/internal/ircserver/commands.go b/internal/ircserver/commands.go
index fb2e8c5..f7ffa04 100644
--- a/internal/ircserver/commands.go
+++ b/internal/ircserver/commands.go
@@ -710,12 +710,12 @@ func (c *Conn) applyChannelModes(
 
 // handleUserMode handles MODE for a nick: a query without a
 // mode string, otherwise a change. Only the client's own
-// nick, in any letter case, is allowed.
+// nick is allowed.
 func (c *Conn) handleUserMode(
 	ctx context.Context,
 	msg *Message,
 ) {
-	if !strings.EqualFold(msg.Params[0], c.currentNick()) {
+	if msg.Params[0] != c.currentNick() {
 		c.sendNumeric(
 			irc.ErrUsersDoNotMatch,
 			"Can't change mode for other users",
diff --git a/internal/ircserver/integration_test.go b/internal/ircserver/integration_test.go
index 3646832..2dde41f 100644
--- a/internal/ircserver/integration_test.go
+++ b/internal/ircserver/integration_test.go
@@ -1084,9 +1084,9 @@ func TestIntegrationWallops(t *testing.T) {
 }
 
 // TestIntegrationUserMode covers MODE for a nick: changes
-// and queries of your own modes in any letter case, refusal
-// for another nick, and a rejected mode string changing
-// nothing.
+// and queries of your own modes, refusal for another nick,
+// even one that differs from yours only in letter case, and
+// a rejected mode string changing nothing.
 func TestIntegrationUserMode(t *testing.T) {
 	t.Parallel()
 
@@ -1106,7 +1106,9 @@ func TestIntegrationUserMode(t *testing.T) {
 	for _, step := range []struct {
 		line, want string
 	}{
-		{"MODE ALICE +w", " 221 alice +w"},
+		{"MODE alice +w", " 221 alice +w"},
+		{"MODE Alice", notYours},
+		{"MODE Alice -w", notYours},
 		{"MODE bob", notYours},
 		{"MODE bob -w", notYours},
 		{"MODE alice xw", unknown},
diff --git a/internal/ircserver/relay.go b/internal/ircserver/relay.go
index 844e705..0dee85b 100644
--- a/internal/ircserver/relay.go
+++ b/internal/ircserver/relay.go
@@ -195,7 +195,7 @@ func (c *Conn) deliverTextMessage(
 	c.mu.Unlock()
 
 	// Don't echo our own messages back.
-	if strings.EqualFold(from, nick) {
+	if from == nick {
 		return
 	}
 
@@ -217,7 +217,7 @@ func (c *Conn) deliverJoin(msg *db.IRCMessage) {
 
 	// Don't echo our own JOINs (we already sent them
 	// during joinChannel).
-	if strings.EqualFold(msg.From, nick) {
+	if msg.From == nick {
 		return
 	}
 
@@ -233,7 +233,7 @@ func (c *Conn) deliverPart(msg *db.IRCMessage, text string) {
 	nick := c.nick
 	c.mu.Unlock()
 
-	if strings.EqualFold(msg.From, nick) {
+	if msg.From == nick {
 		return
 	}
 
@@ -258,7 +258,7 @@ func (c *Conn) deliverNickChange(
 	nick := c.nick
 	c.mu.Unlock()
 
-	if strings.EqualFold(msg.From, nick) {
+	if msg.From == nick {
 		return
 	}
 
@@ -276,7 +276,7 @@ func (c *Conn) deliverQuitMsg(
 	nick := c.nick
 	c.mu.Unlock()
 
-	if strings.EqualFold(msg.From, nick) {
+	if msg.From == nick {
 		return
 	}
 
diff --git a/internal/ircserver/relay_test.go b/internal/ircserver/relay_test.go
index 579d422..caf0cc8 100644
--- a/internal/ircserver/relay_test.go
+++ b/internal/ircserver/relay_test.go
@@ -185,3 +185,39 @@ func TestRelayLineBreaks(t *testing.T) {
 		t.Errorf("got %q, want %q", got, want)
 	}
 }
+
+// TestRelayNickDiffersOnlyInCase checks that an IRC listener
+// user alice receives a JOIN, PRIVMSG, PART, NICK and QUIT
+// from Alice in a channel they share: nicks are
+// case-sensitive, so Alice is someone else.
+func TestRelayNickDiffersOnlyInCase(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+
+	alice := env.dial(t)
+	alice.register("alice")
+	alice.joinAndDrain("#case")
+
+	capitalAlice := env.dial(t)
+	capitalAlice.register("Alice")
+
+	for _, step := range []struct {
+		line, want string
+	}{
+		{"JOIN #case", ":Alice!Alice@* JOIN #case"},
+		{"PRIVMSG #case :hi there", ":Alice!Alice@* PRIVMSG #case :hi there"},
+		{"PART #case :see you", ":Alice!Alice@* PART #case :see you"},
+		{"JOIN #case", ":Alice!Alice@* JOIN #case"},
+		{"NICK Alicia", ":Alice!Alice@* NICK Alicia"},
+		{"NICK Alice", ":Alicia!Alicia@* NICK Alice"}, // back for QUIT
+		{"QUIT", ":Alice!Alice@* QUIT :Quit: Connection closed"},
+	} {
+		capitalAlice.send(step.line)
+
+		got := alice.readLine()
+		if got != step.want {
+			t.Errorf("%s: got %q, want %q", step.line, got, step.want)
+		}
+	}
+}