diff --git a/src/utils/permalinks/Permalinks.ts b/src/utils/permalinks/Permalinks.ts
index 9ccb3e2915..b9ee13334c 100644
--- a/src/utils/permalinks/Permalinks.ts
+++ b/src/utils/permalinks/Permalinks.ts
@@ -219,12 +219,16 @@ export class RoomPermalinkCreator {
                 const getRegex = (hostname: string): RegExp =>
                     new RegExp("^" + utils.globToRegexp(hostname, false) + "$");
 
-                const denied = aclEvent.getContent<{ deny: string[] }>().deny || [];
-                denied.forEach((h) => bannedHostsRegexps.push(getRegex(h)));
+                const denied = aclEvent.getContent<{ deny: string[] }>().deny;
+                if (Array.isArray(denied)) {
+                    denied.forEach((h) => bannedHostsRegexps.push(getRegex(h)));
+                }
 
-                const allowed = aclEvent.getContent<{ allow: string[] }>().allow || [];
+                const allowed = aclEvent.getContent<{ allow: string[] }>().allow;
                 allowedHostsRegexps = []; // we don't want to use the default rule here
-                allowed.forEach((h) => allowedHostsRegexps.push(getRegex(h)));
+                if (Array.isArray(denied)) {
+                    allowed.forEach((h) => allowedHostsRegexps.push(getRegex(h)));
+                }
             }
         }
         this.bannedHostsRegexps = bannedHostsRegexps;