diff --git a/framework/core/js/admin/dist/app.js b/framework/core/js/admin/dist/app.js
index 2d229046d..a7c1137fe 100644
--- a/framework/core/js/admin/dist/app.js
+++ b/framework/core/js/admin/dist/app.js
@@ -22244,9 +22244,11 @@ System.register('flarum/models/Discussion', ['flarum/Model', 'flarum/utils/mixin
          * @public
          */
         postIds: function postIds() {
-          return this.data.relationships.posts.data.map(function (link) {
+          var posts = this.data.relationships.posts;
+
+          return posts ? posts.data.map(function (link) {
             return link.id;
-          });
+          }) : [];
         }
       });
 
diff --git a/framework/core/js/forum/dist/app.js b/framework/core/js/forum/dist/app.js
index 54c8b1f89..a47abc535 100644
--- a/framework/core/js/forum/dist/app.js
+++ b/framework/core/js/forum/dist/app.js
@@ -21928,7 +21928,7 @@ System.register('flarum/components/DiscussionPage', ['flarum/components/Page', '
             // the specific post that was routed to.
             this.stream = new PostStream({ discussion: discussion, includedPosts: includedPosts });
             this.stream.on('positionChanged', this.positionChanged.bind(this));
-            this.stream.goToNumber(m.route.param('near') || includedPosts[0].number(), true);
+            this.stream.goToNumber(m.route.param('near') || includedPosts[0] && includedPosts[0].number(), true);
           }
 
           /**
@@ -31433,9 +31433,11 @@ System.register('flarum/models/Discussion', ['flarum/Model', 'flarum/utils/mixin
          * @public
          */
         postIds: function postIds() {
-          return this.data.relationships.posts.data.map(function (link) {
+          var posts = this.data.relationships.posts;
+
+          return posts ? posts.data.map(function (link) {
             return link.id;
-          });
+          }) : [];
         }
       });
 
diff --git a/framework/core/js/forum/src/components/DiscussionPage.js b/framework/core/js/forum/src/components/DiscussionPage.js
index e67718570..ab7a014c0 100644
--- a/framework/core/js/forum/src/components/DiscussionPage.js
+++ b/framework/core/js/forum/src/components/DiscussionPage.js
@@ -184,7 +184,7 @@ export default class DiscussionPage extends Page {
     // the specific post that was routed to.
     this.stream = new PostStream({discussion, includedPosts});
     this.stream.on('positionChanged', this.positionChanged.bind(this));
-    this.stream.goToNumber(m.route.param('near') || includedPosts[0].number(), true);
+    this.stream.goToNumber(m.route.param('near') || (includedPosts[0] && includedPosts[0].number()), true);
   }
 
   /**
diff --git a/framework/core/js/lib/models/Discussion.js b/framework/core/js/lib/models/Discussion.js
index bfecc00d0..d4c6c0ee6 100644
--- a/framework/core/js/lib/models/Discussion.js
+++ b/framework/core/js/lib/models/Discussion.js
@@ -98,7 +98,9 @@ Object.assign(Discussion.prototype, {
    * @public
    */
   postIds() {
-    return this.data.relationships.posts.data.map(link => link.id);
+    const posts = this.data.relationships.posts;
+
+    return posts ? posts.data.map(link => link.id) : [];
   }
 });