diff --git a/locale/en.php b/locale/en.php
index a439a45b..c9546472 100644
--- a/locale/en.php
+++ b/locale/en.php
@@ -34,7 +34,7 @@ return [
     'API.Miniflux.Error.InvalidTitle'                                      => 'Invalid feed title',
     'API.Miniflux.Error.InvalidImportCategory'                             => 'Payload contains an invalid category name',
     'API.Miniflux.Error.DuplicateImportCategory'                           => 'Payload contains the same category name twice',
-    'API.Miniflux.Error.FailedImportFeed'                                  => 'Unable to import feed at URL "{url}" (code {code}',
+    'API.Miniflux.Error.FailedImportFeed'                                  => 'Unable to import feed at URL "{url}" (code {code})',
     'API.Miniflux.Error.InvalidImportLabel'                                => 'Payload contains an invalid label name',
 
     'API.TTRSS.Category.Uncategorized'                                     => 'Uncategorized',
diff --git a/tests/cases/Misc/TestHTTP.php b/tests/cases/Misc/TestHTTP.php
index 71eec8c7..fee9a67a 100644
--- a/tests/cases/Misc/TestHTTP.php
+++ b/tests/cases/Misc/TestHTTP.php
@@ -43,9 +43,13 @@ class TestHTTP extends \JKingWeb\Arsse\Test\AbstractTest {
 
     public function provideTypedMessages(): iterable {
         return [
-            ["respEmpty", [422, ['Content-Length' => "0"]],                             new Response(422, ['Content-Length' => "0"])],
-            ["respText",  ["OOK"],                                                      new Response(200, ['Content-Type' => "text/plain; charset=UTF-8"], "OOK")],
-            ["respText",  ["OOK", 201, ['Content-Type' => "application/octet-stream"]], new Response(201, ['Content-Type' => "application/octet-stream"], "OOK")],
+            ["respEmpty", [422, ['Content-Length' => "0"]],                                     new Response(422, ['Content-Length' => "0"])],
+            ["respText",  ["OOK"],                                                              new Response(200, ['Content-Type' => "text/plain; charset=UTF-8"], "OOK")],
+            ["respText",  ["OOK", 201, ['Content-Type' => "application/octet-stream"]],         new Response(201, ['Content-Type' => "application/octet-stream"], "OOK")],
+            ["respJson",  [['ook' => "eek"]],                                                   new Response(200, ['Content-Type' => "application/json"], '{"ook":"eek"}')],
+            ["respJson",  [['ook' => "eek"], 400, ['Content-Type' => "application/feed+json"]], new Response(400, ['Content-Type' => "application/feed+json"], '{"ook":"eek"}')],
+            ["respXml",   ["<html/>"],                                                          new Response(200, ['Content-Type' => "application/xml; charset=UTF-8"], "<html/>")],
+            ["respXml",   ["<html/>", 451, ['Content-Type' => "text/plain", 'Vary' => "ETag"]], new Response(451, ['Content-Type' => "text/plain", 'Vary' => "ETag"], "<html/>")],
         ];
     }
 }
diff --git a/tests/cases/REST/Miniflux/TestV1.php b/tests/cases/REST/Miniflux/TestV1.php
index ca4ae1fa..9e3aa3cb 100644
--- a/tests/cases/REST/Miniflux/TestV1.php
+++ b/tests/cases/REST/Miniflux/TestV1.php
@@ -98,6 +98,12 @@ class TestV1 extends \JKingWeb\Arsse\Test\AbstractTest {
         return $value;
     }
 
+    public function testGenerateErrorResponse() {
+        $act = V1::respError(["DuplicateUser", 'user' => "john.doe"], 409, ['Cache-Control' => "no-store"]);
+        $exp = HTTP::respJson(['error_message' => 'The user name "john.doe" already exists'], 409, ['Cache-Control' => "no-store"]);
+        $this->assertMessage($exp, $act);
+    }
+
     /** @dataProvider provideAuthResponses */
     public function testAuthenticateAUser($token, bool $auth, bool $success): void {
         $exp = $success ? HTTP::respEmpty(404) : V1::respError("401", 401);