diff --git a/Iceshrimp.Backend/Controllers/Attributes/MediaTypeRouteFilterAttribute.cs b/Iceshrimp.Backend/Controllers/Attributes/MediaTypeRouteFilterAttribute.cs
index 2b92683b..10785c08 100644
--- a/Iceshrimp.Backend/Controllers/Attributes/MediaTypeRouteFilterAttribute.cs
+++ b/Iceshrimp.Backend/Controllers/Attributes/MediaTypeRouteFilterAttribute.cs
@@ -1,5 +1,6 @@
 using System.Net.Http.Headers;
 using Microsoft.AspNetCore.Mvc.ActionConstraints;
+using Microsoft.Net.Http.Headers;
 
 namespace Iceshrimp.Backend.Controllers.Attributes;
 
@@ -8,6 +9,9 @@ public class MediaTypeRouteFilterAttribute(params string[] mediaTypes) : Attribu
 {
 	public bool Accept(ActionConstraintContext context)
 	{
+		// Add Vary: Accept to the response headers to prevent caches serving the wrong response
+		context.RouteContext.HttpContext.Response.Headers.Append(HeaderNames.Vary, HeaderNames.Accept);
+
 		if (!context.RouteContext.HttpContext.Request.Headers.ContainsKey("Accept")) return false;
 
 		var accept = context.RouteContext.HttpContext.Request.Headers.Accept.ToString()