diff --git a/PluralKit.API/APIJsonExt.cs b/PluralKit.API/APIJsonExt.cs
index d906ff2a..796a17c1 100644
--- a/PluralKit.API/APIJsonExt.cs
+++ b/PluralKit.API/APIJsonExt.cs
@@ -1,3 +1,5 @@
+using Microsoft.AspNetCore.Http;
+
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 
@@ -37,6 +39,13 @@ public static class APIJsonExt
 
         return o;
     }
+
+    public static async Task WriteJSON(this HttpResponse resp, int statusCode, string jsonText)
+    {
+        resp.StatusCode = statusCode;
+        resp.Headers.Add("content-type", "application/json");
+        await resp.WriteAsync(jsonText);
+    }
 }
 
 public struct FrontersReturnNew
diff --git a/PluralKit.API/Startup.cs b/PluralKit.API/Startup.cs
index 06c7b6b8..c935e690 100644
--- a/PluralKit.API/Startup.cs
+++ b/PluralKit.API/Startup.cs
@@ -107,31 +107,19 @@ public class Startup
 
             // handle common ISEs that are generated by invalid user input
             if (exc.Error.IsUserError())
-            {
-                ctx.Response.StatusCode = 400;
-                await ctx.Response.WriteAsync("{\"message\":\"400: Bad Request\",\"code\":0}");
-            }
+                await ctx.Response.WriteJSON(400, "{\"message\":\"400: Bad Request\",\"code\":0}");
 
             else if (exc.Error is not PKError)
-            {
-                ctx.Response.StatusCode = 500;
-                await ctx.Response.WriteAsync("{\"message\":\"500: Internal Server Error\",\"code\":0}");
-            }
+                await ctx.Response.WriteJSON(500, "{\"message\":\"500: Internal Server Error\",\"code\":0}");
 
             // for some reason, if we don't specifically cast to ModelParseError, it uses the base's ToJson method
             else if (exc.Error is ModelParseError fe)
-            {
-                ctx.Response.StatusCode = fe.ResponseCode;
-                await ctx.Response.WriteAsync(JsonConvert.SerializeObject(fe.ToJson()));
-            }
+                await ctx.Response.WriteJSON(fe.ResponseCode, JsonConvert.SerializeObject(fe.ToJson()));
 
             else
             {
                 var err = (PKError)exc.Error;
-                ctx.Response.StatusCode = err.ResponseCode;
-
-                var json = JsonConvert.SerializeObject(err.ToJson());
-                await ctx.Response.WriteAsync(json);
+                await ctx.Response.WriteJSON(err.ResponseCode, JsonConvert.SerializeObject(err.ToJson()));
             }
 
             await ctx.Response.CompleteAsync();