diff --git a/core/ResponseDefinitions.php b/core/ResponseDefinitions.php
index 4a79c3ad3ec85..5c1a22dde0286 100644
--- a/core/ResponseDefinitions.php
+++ b/core/ResponseDefinitions.php
@@ -70,7 +70,7 @@
  *
  * @psalm-type CoreResource = array{
  *     richObjectType: string,
- *     richObject: array<string, mixed>,
+ *     richObject: array<string, ?mixed>,
  *     openGraphObject: CoreOpenGraphObject,
  *     accessible: bool,
  * }
@@ -83,7 +83,7 @@
  *
  * @psalm-type CoreReference = array{
  *     richObjectType: string,
- *     richObject: array<string, mixed>,
+ *     richObject: array<string, ?mixed>,
  *     openGraphObject: CoreOpenGraphObject,
  *     accessible: bool,
  * }
diff --git a/core/openapi.json b/core/openapi.json
index 34009e38472d7..28210059fe10b 100644
--- a/core/openapi.json
+++ b/core/openapi.json
@@ -358,7 +358,8 @@
                     "richObject": {
                         "type": "object",
                         "additionalProperties": {
-                            "type": "object"
+                            "type": "object",
+                            "nullable": true
                         }
                     },
                     "openGraphObject": {
@@ -416,7 +417,8 @@
                     "richObject": {
                         "type": "object",
                         "additionalProperties": {
-                            "type": "object"
+                            "type": "object",
+                            "nullable": true
                         }
                     },
                     "openGraphObject": {