diff --git a/file.go b/file.go
index ecfd218..7162886 100644
--- a/file.go
+++ b/file.go
@@ -11,7 +11,7 @@ import (
 // This object represents the contents of a file to be uploaded.
 // Must be posted using multipart/form-data in the usual way that files are uploaded via the browser.
 type InputFile interface {
-	Attach(name string, data map[string]FileReader) (string, error)
+	InputFileOrString
 	justFiles()
 }
 
@@ -19,7 +19,7 @@ type InputFile interface {
 //
 // This object represents a publicly accessible URL to be reused, or a file_id already available on telegram servers.
 type InputString interface {
-	Attach(name string, data map[string]FileReader) (string, error)
+	InputFileOrString
 	justStrings()
 }
 
@@ -28,56 +28,74 @@ type InputString interface {
 // This object represents the contents of a file to be uploaded, or a publicly accessible URL to be reused.
 // Files must be posted using multipart/form-data in the usual way that files are uploaded via the browser.
 type InputFileOrString interface {
-	Attach(name string, data map[string]FileReader) (string, error)
+	Attach(name string, data map[string]FileReader) error
+	getValue() string
 }
 
 var (
-	_ InputFileOrString = FileString{}
-	_ InputString       = FileString{}
+	_ InputFileOrString = &FileString{}
+	_ InputString       = &FileString{}
 
-	_ InputFileOrString = FileReader{}
-	_ InputFile         = FileReader{}
+	_ InputFileOrString = &FileReader{}
+	_ InputFile         = &FileReader{}
 )
 
 type FileString struct {
 	Value string
 }
 
-func (f FileString) justStrings() {}
+func (f *FileString) justStrings() {}
 
-func (f FileString) MarshalJSON() ([]byte, error) {
-	return json.Marshal(f.Value)
+func (f *FileString) MarshalJSON() ([]byte, error) {
+	return json.Marshal(f.getValue())
 }
 
-func (f FileString) Attach(_ string, _ map[string]FileReader) (string, error) {
-	return f.Value, nil
+func (f *FileString) Attach(_ string, _ map[string]FileReader) error {
+	return nil
+}
+
+func (f *FileString) getValue() string {
+	return f.Value
 }
 
 type FileReader struct {
 	Name string
 	Data io.Reader
+
+	value string
+}
+
+func (f *FileReader) MarshalJSON() ([]byte, error) {
+	return json.Marshal(f.getValue())
 }
 
 var ErrAttachmentKeyAlreadyExists = errors.New("key already exists")
 
-func (f FileReader) Attach(key string, data map[string]FileReader) (string, error) {
+func (f *FileReader) justFiles() {}
+
+func (f *FileReader) Attach(key string, data map[string]FileReader) error {
 	if _, ok := data[key]; ok {
-		return "", ErrAttachmentKeyAlreadyExists
+		return ErrAttachmentKeyAlreadyExists
 	}
-	data[key] = f
-	return "attach://" + key, nil
+	f.value = key
+	data[key] = *f
+	return nil
 }
 
-func (f FileReader) justFiles() {}
+// getValue returns the file attach reference for the relevant multipart form.
+// Calling getValue is only valid after having called Attach on this struct.
+func (f *FileReader) getValue() string {
+	return "attach://" + f.value
+}
 
 // InputFileByURL is used to send a file on the internet via a publicly accessible HTTP URL.
 func InputFileByURL(url string) InputFileOrString {
-	return FileString{Value: url}
+	return &FileString{Value: url}
 }
 
 // InputFileByID is used to send a file that is already present on telegram's servers, using its telegram file_id.
 func InputFileByID(fileID string) InputFileOrString {
-	return FileString{Value: fileID}
+	return &FileString{Value: fileID}
 }
 
 // InputFileByReader is used to send a file by a reader interface; such as a filehandle from os.Open(), or from a byte
@@ -96,5 +114,5 @@ func InputFileByID(fileID string) InputFileOrString {
 //
 //	m, err := b.SendDocument(<chat_id>, gotgbot.InputFileByReader("file.txt", strings.NewReader("Some file contents")), nil)
 func InputFileByReader(name string, r io.Reader) InputFile {
-	return FileReader{Name: name, Data: r}
+	return &FileReader{Name: name, Data: r}
 }
diff --git a/gen_methods.go b/gen_methods.go
index 3e6e1cd..005eb8a 100755
--- a/gen_methods.go
+++ b/gen_methods.go
@@ -2925,11 +2925,11 @@ func (bot *Bot) SendAnimation(chatId int64, animation InputFileOrString, opts *S
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if animation != nil {
-		key, err := animation.Attach("animation", data)
+		err := animation.Attach("animation", data)
 		if err != nil {
 			return nil, err
 		}
-		v["animation"] = key
+		v["animation"] = animation.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -2946,11 +2946,11 @@ func (bot *Bot) SendAnimation(chatId int64, animation InputFileOrString, opts *S
 			v["height"] = strconv.FormatInt(opts.Height, 10)
 		}
 		if opts.Thumbnail != nil {
-			key, err := opts.Thumbnail.Attach("thumbnail", data)
+			err := opts.Thumbnail.Attach("thumbnail", data)
 			if err != nil {
 				return nil, err
 			}
-			v["thumbnail"] = key
+			v["thumbnail"] = opts.Thumbnail.getValue()
 		}
 		v["caption"] = opts.Caption
 		v["parse_mode"] = opts.ParseMode
@@ -3042,11 +3042,11 @@ func (bot *Bot) SendAudio(chatId int64, audio InputFileOrString, opts *SendAudio
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if audio != nil {
-		key, err := audio.Attach("audio", data)
+		err := audio.Attach("audio", data)
 		if err != nil {
 			return nil, err
 		}
-		v["audio"] = key
+		v["audio"] = audio.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -3068,11 +3068,11 @@ func (bot *Bot) SendAudio(chatId int64, audio InputFileOrString, opts *SendAudio
 		v["performer"] = opts.Performer
 		v["title"] = opts.Title
 		if opts.Thumbnail != nil {
-			key, err := opts.Thumbnail.Attach("thumbnail", data)
+			err := opts.Thumbnail.Attach("thumbnail", data)
 			if err != nil {
 				return nil, err
 			}
-			v["thumbnail"] = key
+			v["thumbnail"] = opts.Thumbnail.getValue()
 		}
 		v["disable_notification"] = strconv.FormatBool(opts.DisableNotification)
 		v["protect_content"] = strconv.FormatBool(opts.ProtectContent)
@@ -3335,11 +3335,11 @@ func (bot *Bot) SendDocument(chatId int64, document InputFileOrString, opts *Sen
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if document != nil {
-		key, err := document.Attach("document", data)
+		err := document.Attach("document", data)
 		if err != nil {
 			return nil, err
 		}
-		v["document"] = key
+		v["document"] = document.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -3347,11 +3347,11 @@ func (bot *Bot) SendDocument(chatId int64, document InputFileOrString, opts *Sen
 			v["message_thread_id"] = strconv.FormatInt(opts.MessageThreadId, 10)
 		}
 		if opts.Thumbnail != nil {
-			key, err := opts.Thumbnail.Attach("thumbnail", data)
+			err := opts.Thumbnail.Attach("thumbnail", data)
 			if err != nil {
 				return nil, err
 			}
-			v["thumbnail"] = key
+			v["thumbnail"] = opts.Thumbnail.getValue()
 		}
 		v["caption"] = opts.Caption
 		v["parse_mode"] = opts.ParseMode
@@ -3895,11 +3895,11 @@ func (bot *Bot) SendPhoto(chatId int64, photo InputFileOrString, opts *SendPhoto
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if photo != nil {
-		key, err := photo.Attach("photo", data)
+		err := photo.Attach("photo", data)
 		if err != nil {
 			return nil, err
 		}
-		v["photo"] = key
+		v["photo"] = photo.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -4114,11 +4114,11 @@ func (bot *Bot) SendSticker(chatId int64, sticker InputFileOrString, opts *SendS
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if sticker != nil {
-		key, err := sticker.Attach("sticker", data)
+		err := sticker.Attach("sticker", data)
 		if err != nil {
 			return nil, err
 		}
-		v["sticker"] = key
+		v["sticker"] = sticker.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -4296,11 +4296,11 @@ func (bot *Bot) SendVideo(chatId int64, video InputFileOrString, opts *SendVideo
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if video != nil {
-		key, err := video.Attach("video", data)
+		err := video.Attach("video", data)
 		if err != nil {
 			return nil, err
 		}
-		v["video"] = key
+		v["video"] = video.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -4317,11 +4317,11 @@ func (bot *Bot) SendVideo(chatId int64, video InputFileOrString, opts *SendVideo
 			v["height"] = strconv.FormatInt(opts.Height, 10)
 		}
 		if opts.Thumbnail != nil {
-			key, err := opts.Thumbnail.Attach("thumbnail", data)
+			err := opts.Thumbnail.Attach("thumbnail", data)
 			if err != nil {
 				return nil, err
 			}
-			v["thumbnail"] = key
+			v["thumbnail"] = opts.Thumbnail.getValue()
 		}
 		v["caption"] = opts.Caption
 		v["parse_mode"] = opts.ParseMode
@@ -4405,11 +4405,11 @@ func (bot *Bot) SendVideoNote(chatId int64, videoNote InputFileOrString, opts *S
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if videoNote != nil {
-		key, err := videoNote.Attach("video_note", data)
+		err := videoNote.Attach("video_note", data)
 		if err != nil {
 			return nil, err
 		}
-		v["video_note"] = key
+		v["video_note"] = videoNote.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -4423,11 +4423,11 @@ func (bot *Bot) SendVideoNote(chatId int64, videoNote InputFileOrString, opts *S
 			v["length"] = strconv.FormatInt(opts.Length, 10)
 		}
 		if opts.Thumbnail != nil {
-			key, err := opts.Thumbnail.Attach("thumbnail", data)
+			err := opts.Thumbnail.Attach("thumbnail", data)
 			if err != nil {
 				return nil, err
 			}
-			v["thumbnail"] = key
+			v["thumbnail"] = opts.Thumbnail.getValue()
 		}
 		v["disable_notification"] = strconv.FormatBool(opts.DisableNotification)
 		v["protect_content"] = strconv.FormatBool(opts.ProtectContent)
@@ -4501,11 +4501,11 @@ func (bot *Bot) SendVoice(chatId int64, voice InputFileOrString, opts *SendVoice
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if voice != nil {
-		key, err := voice.Attach("voice", data)
+		err := voice.Attach("voice", data)
 		if err != nil {
 			return nil, err
 		}
-		v["voice"] = key
+		v["voice"] = voice.getValue()
 	}
 	if opts != nil {
 		v["business_connection_id"] = opts.BusinessConnectionId
@@ -4722,11 +4722,11 @@ func (bot *Bot) SetChatPhoto(chatId int64, photo InputFile, opts *SetChatPhotoOp
 	data := map[string]FileReader{}
 	v["chat_id"] = strconv.FormatInt(chatId, 10)
 	if photo != nil {
-		key, err := photo.Attach("photo", data)
+		err := photo.Attach("photo", data)
 		if err != nil {
 			return false, err
 		}
-		v["photo"] = key
+		v["photo"] = photo.getValue()
 	}
 
 	var reqOpts *RequestOpts
@@ -5346,11 +5346,11 @@ func (bot *Bot) SetStickerSetThumbnail(name string, userId int64, format string,
 	v["format"] = format
 	if opts != nil {
 		if opts.Thumbnail != nil {
-			key, err := opts.Thumbnail.Attach("thumbnail", data)
+			err := opts.Thumbnail.Attach("thumbnail", data)
 			if err != nil {
 				return false, err
 			}
-			v["thumbnail"] = key
+			v["thumbnail"] = opts.Thumbnail.getValue()
 		}
 	}
 
@@ -5429,11 +5429,11 @@ func (bot *Bot) SetWebhook(url string, opts *SetWebhookOpts) (bool, error) {
 	v["url"] = url
 	if opts != nil {
 		if opts.Certificate != nil {
-			key, err := opts.Certificate.Attach("certificate", data)
+			err := opts.Certificate.Attach("certificate", data)
 			if err != nil {
 				return false, err
 			}
-			v["certificate"] = key
+			v["certificate"] = opts.Certificate.getValue()
 		}
 		v["ip_address"] = opts.IpAddress
 		if opts.MaxConnections != 0 {
@@ -5800,11 +5800,11 @@ func (bot *Bot) UploadStickerFile(userId int64, sticker InputFile, stickerFormat
 	data := map[string]FileReader{}
 	v["user_id"] = strconv.FormatInt(userId, 10)
 	if sticker != nil {
-		key, err := sticker.Attach("sticker", data)
+		err := sticker.Attach("sticker", data)
 		if err != nil {
 			return nil, err
 		}
-		v["sticker"] = key
+		v["sticker"] = sticker.getValue()
 	}
 	v["sticker_format"] = stickerFormat
 
diff --git a/gen_types.go b/gen_types.go
index 17dbd11..4cd5de8 100755
--- a/gen_types.go
+++ b/gen_types.go
@@ -4816,12 +4816,10 @@ func (v InputMediaAnimation) inputMedia() {}
 
 func (v InputMediaAnimation) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.Media != nil {
-		key, err := v.Media.Attach(mediaName, data)
+		err := v.Media.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.Media = FileString{Value: key}
 	}
 
 	return json.Marshal(v)
@@ -4892,12 +4890,10 @@ func (v InputMediaAudio) inputMedia() {}
 
 func (v InputMediaAudio) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.Media != nil {
-		key, err := v.Media.Attach(mediaName, data)
+		err := v.Media.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.Media = FileString{Value: key}
 	}
 
 	return json.Marshal(v)
@@ -4962,12 +4958,10 @@ func (v InputMediaDocument) inputMedia() {}
 
 func (v InputMediaDocument) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.Media != nil {
-		key, err := v.Media.Attach(mediaName, data)
+		err := v.Media.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.Media = FileString{Value: key}
 	}
 
 	return json.Marshal(v)
@@ -5032,12 +5026,10 @@ func (v InputMediaPhoto) inputMedia() {}
 
 func (v InputMediaPhoto) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.Media != nil {
-		key, err := v.Media.Attach(mediaName, data)
+		err := v.Media.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.Media = FileString{Value: key}
 	}
 
 	return json.Marshal(v)
@@ -5117,12 +5109,10 @@ func (v InputMediaVideo) inputMedia() {}
 
 func (v InputMediaVideo) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.Media != nil {
-		key, err := v.Media.Attach(mediaName, data)
+		err := v.Media.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.Media = FileString{Value: key}
 	}
 
 	return json.Marshal(v)
@@ -5180,12 +5170,10 @@ type InputSticker struct {
 
 func (v InputSticker) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.Sticker != nil {
-		key, err := v.Sticker.Attach(mediaName, data)
+		err := v.Sticker.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.Sticker = FileString{Value: key}
 	}
 
 	return json.Marshal(v)
diff --git a/scripts/generate/methods.go b/scripts/generate/methods.go
index dcac2ff..c8d344c 100644
--- a/scripts/generate/methods.go
+++ b/scripts/generate/methods.go
@@ -400,11 +400,11 @@ type readerBranchesData struct {
 // TODO: Make sure this doesn't allow strings, ONLY readers!
 const inputFileBranch = `
 if {{.GoParam}} != nil {
-	key, err := {{.GoParam}}.Attach("{{.Name}}", data)
+	err := {{.GoParam}}.Attach("{{.Name}}", data)
 	if err != nil {
 		return {{.DefaultReturn}}, err
 	}
-	v["{{.Name}}"] = key
+	v["{{.Name}}"] = {{.GoParam}}.getValue()
 }`
 
 const inputParamsBranch = `
diff --git a/scripts/generate/types.go b/scripts/generate/types.go
index af3e28a..6c5d52a 100644
--- a/scripts/generate/types.go
+++ b/scripts/generate/types.go
@@ -91,6 +91,7 @@ func generateTypeDef(d APIDescription, tgType TypeDescription) (string, error) {
 		return "", fmt.Errorf("failed to check if type requires special handling: %w", err)
 	}
 	if ok {
+		// TODO: Investigate if thumbnails need special handling too.
 		err = inputParamsTmpl.Execute(&typeDef, inputParamsMethodData{
 			Type:  tgType.Name,
 			Field: snakeToTitle(fieldName),
@@ -758,12 +759,10 @@ type inputParamsMethodData struct {
 const inputParamsMethod = `
 func (v {{.Type}}) InputParams(mediaName string, data map[string]FileReader) ([]byte, error) {
 	if v.{{.Field}} != nil {
-		key, err := v.{{.Field}}.Attach(mediaName, data)
+		err := v.{{.Field}}.Attach(mediaName, data)
 		if err != nil {
 			return nil, err
 		}
-		// Now that we've attached the file as a piece of data, we can pass in its file reference.
-		v.{{.Field}} = FileString{Value: key}
 	} 
 	
 	return json.Marshal(v)