diff --git a/api/src/email.rs b/api/src/email.rs
index ab213c5..92e888b 100644
--- a/api/src/email.rs
+++ b/api/src/email.rs
@@ -69,26 +69,42 @@ pub fn confirm(brand: &str, accent: &str, logo: &str, account: &str, code: &str)
     }
 }
 
+/// What an inactivity-expiry warning is about.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ExpiryTarget {
+    Account,
+    Channel,
+}
+
+impl ExpiryTarget {
+    fn word(self) -> &'static str {
+        match self {
+            Self::Account => "account",
+            Self::Channel => "channel",
+        }
+    }
+}
+
 // Warn the owner of an account or channel that inactivity will soon expire it.
-// `kind` is "account" or "channel", `remaining` a human span ("7 days"). The
-// remaining span takes the prominent code slot.
-pub fn expiry_warning(brand: &str, accent: &str, logo: &str, kind: &str, name: &str, remaining: &str) -> Mail {
-    let keep = if kind == "channel" {
+// `remaining` is a human span ("7 days") and takes the prominent code slot.
+pub fn expiry_warning(brand: &str, accent: &str, logo: &str, kind: ExpiryTarget, name: &str, remaining: &str) -> Mail {
+    let word = kind.word();
+    let keep = if kind == ExpiryTarget::Channel {
         "To keep it, have a member join the channel before then. Otherwise it will be removed."
     } else {
         "To keep it, just identify to it before then. Otherwise it will be removed."
     };
     Mail {
-        subject: format!("Your {kind} {name} is about to expire"),
+        subject: format!("Your {word} {name} is about to expire"),
         text: format!(
-            "Your {kind} {name} has been inactive and will expire in {remaining}.\n{keep}\n"
+            "Your {word} {name} has been inactive and will expire in {remaining}.\n{keep}\n"
         ),
         html: render(
             brand,
             accent,
             logo,
             "About to expire",
-            &format!("Your {kind} {name} has been inactive and will expire in {remaining}."),
+            &format!("Your {word} {name} has been inactive and will expire in {remaining}."),
             remaining,
             keep,
         ),
diff --git a/modules/gameserv/src/board.rs b/modules/gameserv/src/board.rs
index d1c8f44..c6e9de7 100644
--- a/modules/gameserv/src/board.rs
+++ b/modules/gameserv/src/board.rs
@@ -289,11 +289,10 @@ pub fn terminal(g: &Game) -> Option<Outcome> {
             }
             full_or_ongoing(b)
         }
-        Board::Chess(st) => match chess::over(st).as_str() {
-            "w" => Some(Outcome::Win(Side::A)),
-            "b" => Some(Outcome::Win(Side::B)),
-            "draw" => Some(Outcome::Draw),
-            _ => None,
+        Board::Chess(st) => match chess::over(st) {
+            None => None,
+            Some(chess::Ending::Draw) => Some(Outcome::Draw),
+            Some(chess::Ending::Checkmate(c)) => Some(Outcome::Win(if c == b'w' { Side::A } else { Side::B })),
         },
     }
 }
diff --git a/modules/gameserv/src/chess.rs b/modules/gameserv/src/chess.rs
index e415f53..aa094ab 100644
--- a/modules/gameserv/src/chess.rs
+++ b/modules/gameserv/src/chess.rs
@@ -476,16 +476,24 @@ pub fn legal(st: &State) -> Vec<Move> {
         .collect()
 }
 
-/// `""` ongoing; `"draw"` for stalemate; or the winning side (`"w"`/`"b"`) on
-/// checkmate.
-pub fn over(st: &State) -> String {
+/// How a position has ended.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Ending {
+    Draw,
+    Checkmate(u8), // the winning colour byte: b'w' or b'b'
+}
+
+/// `None` while the side to move still has a legal move; else the ending
+/// (stalemate → `Draw`, checkmate → `Checkmate(winner)`).
+pub fn over(st: &State) -> Option<Ending> {
     if !legal(st).is_empty() {
-        return String::new();
+        return None;
     }
     if in_check(st, st.turn) {
-        return if st.turn == b'w' { "b" } else { "w" }.to_string();
+        Some(Ending::Checkmate(if st.turn == b'w' { b'b' } else { b'w' }))
+    } else {
+        Some(Ending::Draw)
     }
-    "draw".to_string()
 }
 
 fn name_sq(s: i32) -> String {
diff --git a/src/engine/mod.rs b/src/engine/mod.rs
index 90c0b03..3c4ecb3 100644
--- a/src/engine/mod.rs
+++ b/src/engine/mod.rs
@@ -703,14 +703,14 @@ impl Engine {
         if let Some(lead) = self.expire_warn.filter(|_| self.db.email_enabled()) {
             if let Some(ttl) = self.account_ttl {
                 for (account, email, left) in self.db.accounts_to_warn(now, ttl, lead) {
-                    let mail = echo_api::email::expiry_warning(self.db.email_brand(), self.db.email_accent(), self.db.email_logo(), "account", &account, &human_duration(left));
+                    let mail = echo_api::email::expiry_warning(self.db.email_brand(), self.db.email_accent(), self.db.email_logo(), echo_api::email::ExpiryTarget::Account, &account, &human_duration(left));
                     self.emit_irc(NetAction::SendEmail { to: email, subject: mail.subject, text: mail.text, html: Some(mail.html) });
                     self.db.mark_account_warned(&account);
                 }
             }
             if let Some(ttl) = self.channel_ttl {
                 for (channel, email, left) in self.db.channels_to_warn(now, ttl, lead) {
-                    let mail = echo_api::email::expiry_warning(self.db.email_brand(), self.db.email_accent(), self.db.email_logo(), "channel", &channel, &human_duration(left));
+                    let mail = echo_api::email::expiry_warning(self.db.email_brand(), self.db.email_accent(), self.db.email_logo(), echo_api::email::ExpiryTarget::Channel, &channel, &human_duration(left));
                     self.emit_irc(NetAction::SendEmail { to: email, subject: mail.subject, text: mail.text, html: Some(mail.html) });
                     self.db.mark_channel_warned(&channel);
                 }