diff --git a/lib/client.js b/lib/client.js
index 3d1fb90..416b513 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -77,7 +77,10 @@ export default class Client extends EventTarget {
 	autoReconnect = true;
 	reconnectTimeoutID = null;
 	pingIntervalID = null;
-	pendingHistory = Promise.resolve(null);
+	pendingCmds = {
+		WHO: Promise.resolve(null),
+		CHATHISTORY: Promise.resolve(null),
+	};
 	cm = irc.CaseMapping.RFC1459;
 	monitored = new irc.CaseMapMap(null, irc.CaseMapping.RFC1459);
 	pendingLists = new irc.CaseMapMap(null, irc.CaseMapping.RFC1459);
@@ -126,7 +129,9 @@ export default class Client extends EventTarget {
 			this.availableCaps = {};
 			this.enabledCaps = {};
 			this.batches = new Map();
-			this.pendingHistory = Promise.resolve(null);
+			Object.keys(this.pendingCmds).forEach((k) => {
+				this.pendingCmds[k] = Promise.resolve(null);
+			});
 			this.isupport = new Map();
 			this.monitored = new irc.CaseMapMap(null, irc.CaseMapping.RFC1459);
 
@@ -394,27 +399,30 @@ export default class Client extends EventTarget {
 
 		let msg = { command: "WHO", params };
 		let l = [];
-		return this.roundtrip(msg, (msg) => {
-			switch (msg.command) {
-			case irc.RPL_WHOREPLY:
-				// TODO: match with mask
-				l.push(this.parseWhoReply(msg));
-				break;
-			case irc.RPL_WHOSPCRPL:
-				if (msg.params.length !== fields.length || msg.params[1] !== token) {
+		let promise = this.pendingCmds.WHO.then(() => {
+			return this.roundtrip(msg, (msg) => {
+				switch (msg.command) {
+				case irc.RPL_WHOREPLY:
+					l.push(this.parseWhoReply(msg));
+					break;
+				case irc.RPL_WHOSPCRPL:
+					if (msg.params.length !== fields.length || msg.params[1] !== token) {
+						break;
+					}
+					l.push(this.parseWhoReply(msg));
+					break;
+				case irc.RPL_ENDOFWHO:
+					if (msg.params[1] === mask) {
+						return l;
+					}
 					break;
 				}
-				l.push(this.parseWhoReply(msg));
-				break;
-			case irc.RPL_ENDOFWHO:
-				if (msg.params[1] === mask) {
-					return l;
-				}
-				break;
-			}
-		}).finally(() => {
-			this.whoxQueries.delete(token);
+			}).finally(() => {
+				this.whoxQueries.delete(token);
+			});
 		});
+		this.pendingCmds.WHO = promise.catch(() => {});
+		return promise;
 	}
 
 	parseWhoReply(msg) {
@@ -741,14 +749,15 @@ export default class Client extends EventTarget {
 	roundtripChatHistory(params) {
 		// Don't send multiple CHATHISTORY commands in parallel, we can't
 		// properly handle batches and errors.
-		this.pendingHistory = this.pendingHistory.catch(() => {}).then(() => {
+		let promise = this.pendingCmds.CHATHISTORY.then(() => {
 			let msg = {
 				command: "CHATHISTORY",
 				params,
 			};
 			return this.fetchBatch(msg, "chathistory").then((batch) => batch.messages);
 		});
-		return this.pendingHistory;
+		this.pendingCmds.CHATHISTORY = promise.catch(() => {});
+		return promise;
 	}
 
 	chatHistoryPageSize() {