diff --git a/pkg/captcha/db.go b/pkg/captcha/db.go
index b9fa5e7..c58da36 100644
--- a/pkg/captcha/db.go
+++ b/pkg/captcha/db.go
@@ -37,7 +37,7 @@ type ICaptchaDB interface {
 type CaptchaDB struct {
 	DB       map[ID]ICaptcha
 	ExpireIn time.Duration
-	mut      sync.Mutex
+	sync.Mutex
 }
 
 // SetExpiry stores expire value and starts a goroutine
@@ -68,8 +68,8 @@ func (cdb *CaptchaDB) SetExpiry(expire time.Duration) {
 func (cdb *CaptchaDB) New(data string, captcha ICaptcha) (ICaptcha, ID) {
 	id := NewID(data, captcha.GetAnswer())
 
-	cdb.mut.Lock()
-	defer cdb.mut.Unlock()
+	cdb.Lock()
+	defer cdb.Unlock()
 	cdb.DB[id] = captcha
 
 	return captcha, id
@@ -86,8 +86,8 @@ func (cdb *CaptchaDB) Image(id ID) (*image.Image, error) {
 // Solve compares given answer with a stored one and if failed
 // deletes a captcha from database.
 func (cdb *CaptchaDB) Solve(id ID, answer Answer) (bool, error) {
-	cdb.mut.Lock()
-	defer cdb.mut.Unlock()
+	cdb.Lock()
+	defer cdb.Unlock()
 	if c, ok := cdb.DB[id]; ok {
 		ok = c.Solve(answer)
 		if !ok {
@@ -101,8 +101,8 @@ func (cdb *CaptchaDB) Solve(id ID, answer Answer) (bool, error) {
 // IsSolved checks if captcha was solved and removes it
 // from a database.
 func (cdb *CaptchaDB) IsSolved(id ID) (bool, error) {
-	cdb.mut.Lock()
-	defer cdb.mut.Unlock()
+	cdb.Lock()
+	defer cdb.Unlock()
 	if c, ok := cdb.DB[id]; ok {
 		ok = c.IsSolved()
 		delete(cdb.DB, id)