diff --git a/lib/client.js b/lib/client.js
index 5b471a5..894e991 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -49,6 +49,20 @@ const WHOX_FIELDS = {
 let lastLabel = 0;
 let lastWhoxToken = 0;
 
+class IRCError extends Error {
+	constructor(msg) {
+		let text;
+		if (irc.isError(msg.command) && msg) {
+			text = msg.params[msg.params.length - 1];
+		} else {
+			text = `unknown error (${msg.command} ${msg.params.join(" ")})`;
+		}
+		super(text);
+
+		this.msg = msg;
+	}
+}
+
 export default class Client extends EventTarget {
 	static Status = {
 		DISCONNECTED: "disconnected",
@@ -412,7 +426,7 @@ export default class Client extends EventTarget {
 			case irc.ERR_SASLTOOLONG:
 			case irc.ERR_SASLABORTED:
 			case irc.ERR_SASLALREADY:
-				throw msg;
+				throw new IRCError(msg);
 			}
 		});
 		this.send(initialResp);
@@ -528,7 +542,7 @@ export default class Client extends EventTarget {
 			case irc.ERR_NOSUCHNICK:
 				nick = msg.params[1];
 				if (this.cm(nick) === targetCM) {
-					throw msg;
+					throw new IRCError(msg);
 				}
 				break;
 			}
@@ -784,7 +798,7 @@ export default class Client extends EventTarget {
 				break;
 			case "FAIL":
 				if (msg.params[0] === cmd) {
-					throw msg;
+					throw new IRCError(msg);
 				}
 				break;
 			}
@@ -946,7 +960,7 @@ export default class Client extends EventTarget {
 				};
 			case "FAIL":
 				if (msg.params[0] === "REGISTER") {
-					throw msg;
+					throw new IRCError(msg);
 				}
 				break;
 			}
@@ -964,7 +978,7 @@ export default class Client extends EventTarget {
 				return { message: msg.params[2] };
 			case "FAIL":
 				if (msg.params[0] === "VERIFY") {
-					throw msg;
+					throw new IRCError(msg);
 				}
 				break;
 			}