diff --git a/fs.go b/fs.go
index f17d7434d9..51c3db86fb 100644
--- a/fs.go
+++ b/fs.go
@@ -9,37 +9,43 @@ import (
 	"os"
 )
 
-type onlyFilesFS struct {
-	fs http.FileSystem
+// OnlyFilesFS implements an http.FileSystem without `Readdir` functionality.
+type OnlyFilesFS struct {
+	FileSystem http.FileSystem
 }
 
-type neuteredReaddirFile struct {
+// Open passes `Open` to the upstream implementation without `Readdir` functionality.
+func (o OnlyFilesFS) Open(name string) (http.File, error) {
+	f, err := o.FileSystem.Open(name)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return neutralizedReaddirFile{f}, nil
+}
+
+// neutralizedReaddirFile wraps http.File with a specific implementation of `Readdir`.
+type neutralizedReaddirFile struct {
 	http.File
 }
 
-// Dir returns a http.FileSystem that can be used by http.FileServer(). It is used internally
-// in router.Static().
-// if listDirectory == true, then it works the same as http.Dir() otherwise it returns
-// a filesystem that prevents http.FileServer() to list the directory files.
+// Readdir overrides the http.File default implementation and always returns nil.
+func (n neutralizedReaddirFile) Readdir(_ int) ([]os.FileInfo, error) {
+	// this disables directory listing
+	return nil, nil
+}
+
+// Dir returns an http.FileSystem that can be used by http.FileServer().
+// It is used internally in router.Static().
+// if listDirectory == true, then it works the same as http.Dir(),
+// otherwise it returns a filesystem that prevents http.FileServer() to list the directory files.
 func Dir(root string, listDirectory bool) http.FileSystem {
 	fs := http.Dir(root)
+
 	if listDirectory {
 		return fs
 	}
-	return &onlyFilesFS{fs}
-}
-
-// Open conforms to http.Filesystem.
-func (fs onlyFilesFS) Open(name string) (http.File, error) {
-	f, err := fs.fs.Open(name)
-	if err != nil {
-		return nil, err
-	}
-	return neuteredReaddirFile{f}, nil
-}
 
-// Readdir overrides the http.File default implementation.
-func (f neuteredReaddirFile) Readdir(_ int) ([]os.FileInfo, error) {
-	// this disables directory listing
-	return nil, nil
+	return &OnlyFilesFS{FileSystem: fs}
 }
diff --git a/fs_test.go b/fs_test.go
new file mode 100644
index 0000000000..a1690cd928
--- /dev/null
+++ b/fs_test.go
@@ -0,0 +1,71 @@
+package gin
+
+import (
+	"errors"
+	"net/http"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type mockFileSystem struct {
+	open func(name string) (http.File, error)
+}
+
+func (m *mockFileSystem) Open(name string) (http.File, error) {
+	return m.open(name)
+}
+
+func TestOnlyFilesFS_Open(t *testing.T) {
+	var testFile *os.File
+	mockFS := &mockFileSystem{
+		open: func(name string) (http.File, error) {
+			return testFile, nil
+		},
+	}
+	fs := &OnlyFilesFS{FileSystem: mockFS}
+
+	file, err := fs.Open("foo")
+
+	assert.NoError(t, err)
+	assert.Equal(t, testFile, file.(neutralizedReaddirFile).File)
+}
+
+func TestOnlyFilesFS_Open_err(t *testing.T) {
+	testError := errors.New("mock")
+	mockFS := &mockFileSystem{
+		open: func(_ string) (http.File, error) {
+			return nil, testError
+		},
+	}
+	fs := &OnlyFilesFS{FileSystem: mockFS}
+
+	file, err := fs.Open("foo")
+
+	assert.ErrorIs(t, err, testError)
+	assert.Nil(t, file)
+}
+
+func Test_neuteredReaddirFile_Readdir(t *testing.T) {
+	n := neutralizedReaddirFile{}
+
+	res, err := n.Readdir(0)
+
+	assert.NoError(t, err)
+	assert.Nil(t, res)
+}
+
+func TestDir_listDirectory(t *testing.T) {
+	testRoot := "foo"
+	fs := Dir(testRoot, true)
+
+	assert.Equal(t, http.Dir(testRoot), fs)
+}
+
+func TestDir(t *testing.T) {
+	testRoot := "foo"
+	fs := Dir(testRoot, false)
+
+	assert.Equal(t, &OnlyFilesFS{FileSystem: http.Dir(testRoot)}, fs)
+}
diff --git a/routergroup.go b/routergroup.go
index c833fe8fe3..b2540ec11e 100644
--- a/routergroup.go
+++ b/routergroup.go
@@ -218,7 +218,7 @@ func (group *RouterGroup) createStaticHandler(relativePath string, fs http.FileS
 	fileServer := http.StripPrefix(absolutePath, http.FileServer(fs))
 
 	return func(c *Context) {
-		if _, noListing := fs.(*onlyFilesFS); noListing {
+		if _, noListing := fs.(*OnlyFilesFS); noListing {
 			c.Writer.WriteHeader(http.StatusNotFound)
 		}