diff --git a/api/base_api_controller.go b/api/base_api_controller.go
index 9dd5f6fef..716d0fc44 100644
--- a/api/base_api_controller.go
+++ b/api/base_api_controller.go
@@ -13,6 +13,15 @@ func (c *BaseAPIController) NewEmpty() responses.Subsonic {
 	return responses.Subsonic{Status: "ok", Version: beego.AppConfig.String("apiVersion")}
 }
 
+func (c *BaseAPIController) ValidateParameters(param string, msg string) string {
+	p := c.Input().Get(param)
+	if p == "" {
+		c.SendError(responses.ERROR_MISSING_PARAMETER, msg)
+	}
+	c.Data[param] = p
+	return p
+}
+
 func (c *BaseAPIController) SendError(errorCode int, message ...interface{}) {
 	response := responses.Subsonic{Version: beego.AppConfig.String("apiVersion"), Status: "fail"}
 	var msg string
diff --git a/api/get_cover_art.go b/api/get_cover_art.go
index 9667aca7b..f9e9a876f 100644
--- a/api/get_cover_art.go
+++ b/api/get_cover_art.go
@@ -21,10 +21,7 @@ func (c *GetCoverArtController) Prepare() {
 }
 
 func (c *GetCoverArtController) Get() {
-	id := c.Input().Get("id")
-	if id == "" {
-		c.SendError(responses.ERROR_MISSING_PARAMETER, "id parameter required")
-	}
+	id := c.ValidateParameters("id", "id parameter required")
 
 	mf, err := c.repo.Get(id)
 	if err != nil {
diff --git a/api/get_cover_art_test.go b/api/get_cover_art_test.go
index 6c268addd..8abf473fd 100644
--- a/api/get_cover_art_test.go
+++ b/api/get_cover_art_test.go
@@ -20,7 +20,7 @@ func getCoverArt(params ...string) (*http.Request, *httptest.ResponseRecorder) {
 	r, _ := http.NewRequest("GET", url, nil)
 	w := httptest.NewRecorder()
 	beego.BeeApp.Handlers.ServeHTTP(w, r)
-	beego.Debug("testing TestGetCoverArtDirectory", fmt.Sprintf("\nUrl: %s\nStatus Code: [%d]\n%#v", r.URL, w.Code, w.HeaderMap))
+	beego.Debug("testing TestGetCoverArt", fmt.Sprintf("\nUrl: %s\nStatus Code: [%d]\n%#v", r.URL, w.Code, w.HeaderMap))
 	return r, w
 }
 
diff --git a/api/get_music_directory.go b/api/get_music_directory.go
index 3062dbc9a..fc16d6fa0 100644
--- a/api/get_music_directory.go
+++ b/api/get_music_directory.go
@@ -6,7 +6,6 @@ import (
 	"github.com/deluan/gosonic/domain"
 	"github.com/deluan/gosonic/utils"
 	"github.com/karlkfi/inject"
-	"mime"
 )
 
 type GetMusicDirectoryController struct {
@@ -23,11 +22,7 @@ func (c *GetMusicDirectoryController) Prepare() {
 }
 
 func (c *GetMusicDirectoryController) Get() {
-	id := c.Input().Get("id")
-
-	if id == "" {
-		c.SendError(responses.ERROR_MISSING_PARAMETER, "id parameter required")
-	}
+	id := c.ValidateParameters("id", "id parameter required")
 
 	response := c.NewEmpty()
 
@@ -83,7 +78,7 @@ func (c *GetMusicDirectoryController) buildAlbumDir(al *domain.Album, tracks []d
 		if mf.HasCoverArt {
 			dir.Child[i].CoverArt = mf.Id
 		}
-		dir.Child[i].ContentType = mime.TypeByExtension("." + mf.Suffix)
+		dir.Child[i].ContentType = mf.ContentType()
 	}
 	return dir
 }
diff --git a/domain/mediafile.go b/domain/mediafile.go
index 4aed54416..f5b853bff 100644
--- a/domain/mediafile.go
+++ b/domain/mediafile.go
@@ -2,6 +2,7 @@ package domain
 
 import (
 	"time"
+	"mime"
 )
 
 type MediaFile struct {
@@ -27,6 +28,10 @@ type MediaFile struct {
 	UpdatedAt   time.Time
 }
 
+func (mf *MediaFile) ContentType() string {
+	return mime.TypeByExtension("." + mf.Suffix)
+}
+
 type MediaFileRepository interface {
 	BaseRepository
 	Put(m *MediaFile) error