diff --git a/public/openapi/components/schemas/PostObject.yaml b/public/openapi/components/schemas/PostObject.yaml
index 5ff918cd7f..526bc2c75e 100644
--- a/public/openapi/components/schemas/PostObject.yaml
+++ b/public/openapi/components/schemas/PostObject.yaml
@@ -74,6 +74,9 @@ PostObject:
           description: A category identifier
         slug:
           type: string
+        thumb:
+          type: string
+          description: An uploaded topic thumbnail
         deleted:
           type: number
         postcount:
diff --git a/public/openapi/components/schemas/TopicObject.yaml b/public/openapi/components/schemas/TopicObject.yaml
index 10453fe22b..6f2c45cfcf 100644
--- a/public/openapi/components/schemas/TopicObject.yaml
+++ b/public/openapi/components/schemas/TopicObject.yaml
@@ -41,6 +41,9 @@ TopicObject:
       type: number
     locked:
       type: number
+    thumb:
+      type: string
+      description: An uploaded topic thumbnail
     pinned:
       type: number
       description: Whether or not this particular topic is pinned to the top of the
@@ -221,8 +224,6 @@ TopicObject:
         description: HTML injected into the theme
     index:
       type: number
-    thumb:
-      type: string
   required:
     - tid
     - uid
diff --git a/public/openapi/read/topic/tid/id.yaml b/public/openapi/read/topic/tid/id.yaml
index cdc638a1f5..fab2532476 100644
--- a/public/openapi/read/topic/tid/id.yaml
+++ b/public/openapi/read/topic/tid/id.yaml
@@ -42,6 +42,9 @@ get:
                 type: number
               viewcount:
                 type: number
+              thumb:
+                type: string
+                description: An uploaded topic thumbnail
               deleted:
                 type: number
               locked:
diff --git a/public/openapi/read/topic/topic_id.yaml b/public/openapi/read/topic/topic_id.yaml
index c55c6888cd..d293d37ce5 100644
--- a/public/openapi/read/topic/topic_id.yaml
+++ b/public/openapi/read/topic/topic_id.yaml
@@ -53,6 +53,9 @@ get:
                     type: number
                   viewcount:
                     type: number
+                  thumb:
+                    type: string
+                    description: An uploaded topic thumbnail
                   postercount:
                     type: number
                     description: The number of unique users who made a post in this topic
diff --git a/public/openapi/read/unread.yaml b/public/openapi/read/unread.yaml
index a5fe83348e..9af7956705 100644
--- a/public/openapi/read/unread.yaml
+++ b/public/openapi/read/unread.yaml
@@ -49,6 +49,9 @@ get:
                           type: number
                         viewcount:
                           type: number
+                        thumb:
+                          type: string
+                          description: An uploaded topic thumbnail
                         postercount:
                           type: number
                         teaserPid:
diff --git a/src/topics/data.js b/src/topics/data.js
index 720d2e63ad..d33ddb29d0 100644
--- a/src/topics/data.js
+++ b/src/topics/data.js
@@ -98,9 +98,7 @@ function modifyTopic(topic, fields) {
 
 	escapeTitle(topic);
 
-	if (topic.hasOwnProperty('thumb')) {
-		topic.thumb = validator.escape(String(topic.thumb));
-	}
+	topic.thumb = validator.escape(String(topic.thumb)) || '';
 
 	if (topic.hasOwnProperty('timestamp')) {
 		topic.timestampISO = utils.toISOString(topic.timestamp);