diff --git a/changelog.d/110.misc b/changelog.d/110.misc
new file mode 100644
index 00000000..4d9109a0
--- /dev/null
+++ b/changelog.d/110.misc
@@ -0,0 +1 @@
+Include any certfp lines in a whois response.
diff --git a/src/codes.ts b/src/codes.ts
index cadc560e..3fada45b 100644
--- a/src/codes.ts
+++ b/src/codes.ts
@@ -157,6 +157,10 @@ export const replyCodes = {
         name: 'rpl_globalusers',
         type: 'reply'
     },
+    276: {
+        name: 'rpl_whoiscertfp',
+        type: 'reply',
+    },
     300: {
         name: 'rpl_none',
         type: 'reply'
diff --git a/src/irc.ts b/src/irc.ts
index 40c85898..80eb972f 100644
--- a/src/irc.ts
+++ b/src/irc.ts
@@ -1052,6 +1052,8 @@ export class Client extends (EventEmitter as unknown as new () => TypedEmitter<C
                 return this._addWhoisData(message.args[1], 'serverinfo', message.args[3]);
             case 'rpl_whoisactually':
                 return this._addWhoisData(message.args[1], 'realHost', message.args[2]);
+            case 'rpl_whoiscertfp':
+                return this._addWhoisData(message.args[1], 'certfp', message.args[2]);
             case 'rpl_whoisoperator':
                 return this._addWhoisData(message.args[1], 'operator', message.args[2]);
             case 'rpl_whoisaccount':
@@ -1452,6 +1454,7 @@ export class Client extends (EventEmitter as unknown as new () => TypedEmitter<C
      * unmaps the client instance from the socket. The state will also need to be cleared up seperately.
      */
     public destroy() {
+        util.log('Destroying connection');
         (
             ['data', 'end', 'close', 'timeout', 'error'] as (keyof IrcConnectionEventsMap)[]
         ).forEach(evtType => {
@@ -1690,14 +1693,18 @@ export class Client extends (EventEmitter as unknown as new () => TypedEmitter<C
         return this.send('LIST', ...args);
     }
 
-    private _addWhoisData(nick: string, key: keyof(WhoisResponse), value: string|string[], onlyIfExists = false) {
-        if (onlyIfExists && !this.state.whoisData.has(nick)) {return;}
-        const data: WhoisResponse = {
-            ...this.state.whoisData.get(nick),
-            nick,
-            [key]: value,
-        };
-        this.state.whoisData.set(nick, data);
+    private _addWhoisData<
+        K extends keyof(WhoisResponse),
+        V extends WhoisResponse[K]>(nick: string, key: K, value: V, onlyIfExists = false) {
+        let data: WhoisResponse|undefined = this.state.whoisData.get(nick);
+        if (onlyIfExists && !data) {
+            return;
+        }
+        else if (!data) {
+            data = { nick };
+            this.state.whoisData.set(nick, data);
+        }
+        data[key] = value;
     }
 
     private _clearWhoisData(nick: string) {
diff --git a/src/state.ts b/src/state.ts
index d4eae97a..0edd2e04 100644
--- a/src/state.ts
+++ b/src/state.ts
@@ -14,6 +14,7 @@ export interface WhoisResponse {
     account?: string;
     accountinfo?: string;
     realHost?: string;
+    certfp?: string;
 }
 
 export interface IrcSupported {
diff --git a/src/testing/index.ts b/src/testing/index.ts
index e69c03d7..a8638c55 100644
--- a/src/testing/index.ts
+++ b/src/testing/index.ts
@@ -1,5 +1,5 @@
 import { randomUUID } from 'crypto';
-import { Client, ClientEvents, Message } from '..';
+import { Client, ClientEvents, IrcClientOpts, Message } from '..';
 
 const DEFAULT_PORT = parseInt(process.env.IRC_TEST_PORT ?? '6667', 10);
 const DEFAULT_ADDRESS = process.env.IRC_TEST_ADDRESS ?? "127.0.0.1";
@@ -75,7 +75,10 @@ export class TestIrcServer {
     }
 
     public readonly clients: Record<string, TestClient> = {};
-    constructor(public readonly address = DEFAULT_ADDRESS, public readonly port = DEFAULT_PORT) { }
+    constructor(
+        public readonly address = DEFAULT_ADDRESS, public readonly port = DEFAULT_PORT,
+        public readonly customConfig: Partial<IrcClientOpts> = {}
+    ) { }
 
     async setUp(clients = ['speaker', 'listener']) {
         const connections: Promise<void>[] = [];
@@ -86,6 +89,7 @@ export class TestIrcServer {
                     autoConnect: false,
                     connectionTimeout: 4000,
                     debug: true,
+                    ...this.customConfig,
                 });
             this.clients[clientName] = client;
             // Make sure we load isupport before reporting readyness.