diff --git a/src/server/app.ts b/src/server/app.ts
index 1f679f7..e7bc812 100644
--- a/src/server/app.ts
+++ b/src/server/app.ts
@@ -85,9 +85,15 @@ export function buildApp() {
 						},
 					});
 				}
+				if (error.statusCode >= 500) {
+					console.error("AppError(" + error.statusCode + "):", error);
+				}
 				return new Response(error.message, {
 					status: error.statusCode,
-					headers: { "cache-control": PRIVATE_CACHE },
+					headers: {
+						"cache-control": PRIVATE_CACHE,
+						"content-type": "text/plain; charset=utf-8",
+					},
 				});
 			}
 			if (code === "NOT_FOUND") {