diff --git a/server/server.go b/server/server.go
index 996a6d4a..d424c1b9 100644
--- a/server/server.go
+++ b/server/server.go
@@ -96,6 +96,8 @@ const (
 	defaultAttachmentMessage = "You received a file: %s" // Used if message body is empty, and there is an attachment
 	encodingBase64           = "base64"
 	encodingJWE              = "jwe"
+	multipartFieldMessage    = "message"
+	multipartFieldAttachment = "attachment"
 )
 
 // WebSocket constants
@@ -539,8 +541,8 @@ func (s *Server) handlePublishEncrypted(r *http.Request, m *message) (body *util
 		p, err := mp.NextPart()
 		if err != nil {
 			return nil, err
-		} else if p.FormName() != "message" {
-			return nil, errHTTPBadRequestUnexpectedMultipartField
+		} else if p.FormName() != multipartFieldMessage {
+			return nil, wrapErrHTTP(errHTTPBadRequestUnexpectedMultipartField, "expected '%s', got '%s'", multipartFieldMessage, p.FormName())
 		}
 		messageBody, err := util.PeekLimit(p, s.config.MessageLimit)
 		if err == util.ErrLimitReached {
@@ -552,11 +554,11 @@ func (s *Server) handlePublishEncrypted(r *http.Request, m *message) (body *util
 		p, err = mp.NextPart()
 		if err != nil {
 			return nil, err
-		} else if p.FormName() != "attachment" {
-			return nil, errHTTPBadRequestUnexpectedMultipartField
+		} else if p.FormName() != multipartFieldAttachment {
+			return nil, wrapErrHTTP(errHTTPBadRequestUnexpectedMultipartField, "expected '%s', got '%s'", multipartFieldAttachment, p.FormName())
 		}
 		m.Attachment = &attachment{
-			Name: "attachment.jwe", // Force handlePublishBody into "attachment" mode
+			Name: "attachment.jwe", // Force handlePublishBody into "attachment" mode; .jwe forces application/jose type
 		}
 		body, err = util.Peek(p, s.config.MessageLimit)
 		if err != nil {
diff --git a/server/server_test.go b/server/server_test.go
index 0384e78c..9edbd9e7 100644
--- a/server/server_test.go
+++ b/server/server_test.go
@@ -1487,9 +1487,9 @@ func TestServer_PublishEncrypted_Simple_TooLarge(t *testing.T) {
 
 func TestServer_PublishEncrypted_WithAttachment(t *testing.T) {
 	s := newTestServer(t, newTestConfig(t))
-	parts := map[string]string{
-		"message":    "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..gSRYZeX6eBhlj13w.LOchcxFXwALXE2GqdoSwFJEXdMyEbLfLKV9geXr17WrAN-nH7ya1VQ_Y6ebT1w.2eyLaTUfc_rpKaZr4-5I1Q",
-		"attachment": "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..vbe1Qv_-mKYbUgce.EfmOUIUi7lxXZG_o4bqXZ9pmpr1Rzs4Y5QLE2XD2_aw_SQ.y2hadrN5b2LEw7_PJHhbcA",
+	parts := []mpart{
+		{"message", "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..gSRYZeX6eBhlj13w.LOchcxFXwALXE2GqdoSwFJEXdMyEbLfLKV9geXr17WrAN-nH7ya1VQ_Y6ebT1w.2eyLaTUfc_rpKaZr4-5I1Q"},
+		{"attachment", "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..vbe1Qv_-mKYbUgce.EfmOUIUi7lxXZG_o4bqXZ9pmpr1Rzs4Y5QLE2XD2_aw_SQ.y2hadrN5b2LEw7_PJHhbcA"},
 	}
 	response := requestMultipart(t, s, "PUT", "/mytopic", parts, map[string]string{
 		"Encoding": "jwe",
@@ -1506,6 +1506,37 @@ func TestServer_PublishEncrypted_WithAttachment(t *testing.T) {
 	require.Equal(t, "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..vbe1Qv_-mKYbUgce.EfmOUIUi7lxXZG_o4bqXZ9pmpr1Rzs4Y5QLE2XD2_aw_SQ.y2hadrN5b2LEw7_PJHhbcA", readFile(t, file))
 }
 
+func TestServer_PublishEncrypted_WithAttachment_TooLarge_Attachment(t *testing.T) {
+	c := newTestConfig(t)
+	c.AttachmentFileSizeLimit = 5000
+	s := newTestServer(t, c)
+	parts := []mpart{
+		{"message", "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..gSRYZeX6eBhlj13w.LOchcxFXwALXE2GqdoSwFJEXdMyEbLfLKV9geXr17WrAN-nH7ya1VQ_Y6ebT1w.2eyLaTUfc_rpKaZr4-5I1Q"},
+		{"attachment", strings.Repeat("a", 5001)}, // > 5000
+	}
+	response := requestMultipart(t, s, "PUT", "/mytopic", parts, map[string]string{
+		"Encoding": "jwe",
+	})
+	err := toHTTPError(t, response.Body.String())
+	require.Equal(t, 413, err.HTTPCode)
+	require.Equal(t, 41301, err.Code)
+}
+
+func TestServer_PublishEncrypted_WithAttachment_TooLarge_Message(t *testing.T) {
+	s := newTestServer(t, newTestConfig(t))
+	parts := []mpart{
+		{"message", strings.Repeat("a", 5000)},
+		{"attachment", "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..gSRYZeX6eBhlj13w.LOchcxFXwALXE2GqdoSwFJEXdMyEbLfLKV9geXr17WrAN-nH7ya1VQ_Y6ebT1w.2eyLaTUfc_rpKaZr4-5I1Q"},
+	}
+	response := requestMultipart(t, s, "PUT", "/mytopic", parts, map[string]string{
+		"Encoding": "jwe",
+	})
+	err := toHTTPError(t, response.Body.String())
+	log.Printf(err.Error())
+	require.Equal(t, 413, err.HTTPCode)
+	require.Equal(t, 41303, err.Code)
+}
+
 func newTestConfig(t *testing.T) *Config {
 	conf := NewConfig()
 	conf.BaseURL = "http://127.0.0.1:12345"
@@ -1536,12 +1567,16 @@ func request(t *testing.T, s *Server, method, url, body string, headers map[stri
 	return rr
 }
 
-func requestMultipart(t *testing.T, s *Server, method, url string, parts map[string]string, headers map[string]string) *httptest.ResponseRecorder {
+type mpart struct {
+	key, value string
+}
+
+func requestMultipart(t *testing.T, s *Server, method, url string, parts []mpart, headers map[string]string) *httptest.ResponseRecorder {
 	var b bytes.Buffer
 	w := multipart.NewWriter(&b)
-	for k, v := range parts {
-		mw, _ := w.CreateFormField(k)
-		_, err := io.Copy(mw, strings.NewReader(v))
+	for _, part := range parts {
+		mw, _ := w.CreateFormField(part.key)
+		_, err := io.Copy(mw, strings.NewReader(part.value))
 		require.Nil(t, err)
 	}
 	require.Nil(t, w.Close())