diff --git a/src/Module/ActivityPub/Objects.php b/src/Module/ActivityPub/Objects.php
index 34d460951..2d5862a1c 100644
--- a/src/Module/ActivityPub/Objects.php
+++ b/src/Module/ActivityPub/Objects.php
@@ -130,6 +130,8 @@ class Objects extends BaseModule
 		// Relaxed CORS header for public items
 		header('Access-Control-Allow-Origin: *');
 
+		header('Vary: Accept', false);
+
 		System::jsonExit($data, 'application/activity+json');
 	}
 }
diff --git a/src/Module/Friendica.php b/src/Module/Friendica.php
index 90869878e..739078763 100644
--- a/src/Module/Friendica.php
+++ b/src/Module/Friendica.php
@@ -90,6 +90,8 @@ class Friendica extends BaseModule
 			$blocked = null;
 		}
 
+		header('Vary: Accept', false);
+
 		$hooked = '';
 
 		Hook::callAll('about_hook', $hooked);
@@ -125,6 +127,7 @@ class Friendica extends BaseModule
 				$data = ActivityPub\Transmitter::getProfile(0);
 				header('Access-Control-Allow-Origin: *');
 				header('Cache-Control: max-age=23200, stale-while-revalidate=23200');
+				header('Vary: Accept', false);
 				System::jsonExit($data, 'application/activity+json');
 			} catch (HTTPException\NotFoundException $e) {
 				System::jsonError(404, ['error' => 'Record not found']);
diff --git a/src/Module/Item/Display.php b/src/Module/Item/Display.php
index b2ed43c5b..54e55de2f 100644
--- a/src/Module/Item/Display.php
+++ b/src/Module/Item/Display.php
@@ -162,6 +162,8 @@ class Display extends BaseModule
 
 		$output .= $this->getDisplayData($item);
 
+		header('Vary: Accept', false);
+
 		return $output;
 	}
 
diff --git a/src/Module/Profile/Profile.php b/src/Module/Profile/Profile.php
index 5e5028cb8..b8f16656e 100644
--- a/src/Module/Profile/Profile.php
+++ b/src/Module/Profile/Profile.php
@@ -87,6 +87,7 @@ class Profile extends BaseProfile
 					$data = ActivityPub\Transmitter::getProfile($user['uid']);
 					header('Access-Control-Allow-Origin: *');
 					header('Cache-Control: max-age=23200, stale-while-revalidate=23200');
+					header('Vary: Accept', false);
 					System::jsonExit($data, 'application/activity+json');
 				} catch (HTTPException\NotFoundException $e) {
 					System::jsonError(404, ['error' => 'Record not found']);
@@ -103,6 +104,8 @@ class Profile extends BaseProfile
 				System::jsonError(404, []);
 			}
 		}
+
+		header('Vary: Accept', false);
 	}
 
 	protected function content(array $request = []): string
diff --git a/src/Module/Xrd.php b/src/Module/Xrd.php
index 6a4c0e860..71a3d37a9 100644
--- a/src/Module/Xrd.php
+++ b/src/Module/Xrd.php
@@ -152,6 +152,7 @@ class Xrd extends BaseModule
 			]
 		];
 		header('Access-Control-Allow-Origin: *');
+		header('Vary: Accept', false);
 		System::jsonExit($json, 'application/jrd+json; charset=utf-8');
 	}
 
@@ -229,6 +230,7 @@ class Xrd extends BaseModule
 		];
 
 		header('Access-Control-Allow-Origin: *');
+		header('Vary: Accept', false);
 		System::jsonExit($json, 'application/jrd+json; charset=utf-8');
 	}
 
@@ -326,7 +328,7 @@ class Xrd extends BaseModule
 		]);
 
 		header('Access-Control-Allow-Origin: *');
-
+		header('Vary: Accept', false);
 		System::httpExit($xmlString, Response::TYPE_XML, 'application/xrd+xml');
 	}
 }