diff --git a/core/backend.go b/core/backend.go
index 1fa348b..8be7b82 100644
--- a/core/backend.go
+++ b/core/backend.go
@@ -69,7 +69,7 @@ type Notifier interface {
 type Backend interface {
 	MessageConstructor
 	Verifier
-	validatorBackend
+	ValidatorBackend
 	Notifier
 
 	// BuildProposal builds a new proposal for the given view (height and round)
diff --git a/core/validator_manager.go b/core/validator_manager.go
index 894ab48..139f9fb 100644
--- a/core/validator_manager.go
+++ b/core/validator_manager.go
@@ -13,8 +13,8 @@ var (
 	errVotingPowerNotCorrect = errors.New("total voting power is zero or less")
 )
 
-// validatorBackend defines interface that has GetVotingPower
-type validatorBackend interface {
+// ValidatorBackend defines interface that has GetVotingPower
+type ValidatorBackend interface {
 	// GetVotingPowers returns map of validators addresses and their voting powers for the specified height.
 	GetVotingPowers(height uint64) (map[string]*big.Int, error)
 }
@@ -30,13 +30,13 @@ type ValidatorManager struct {
 	// the height specified in the current View
 	validatorsVotingPower map[string]*big.Int
 
-	backend validatorBackend
+	backend ValidatorBackend
 
 	log Logger
 }
 
 // NewValidatorManager creates new ValidatorManager
-func NewValidatorManager(backend validatorBackend, log Logger) *ValidatorManager {
+func NewValidatorManager(backend ValidatorBackend, log Logger) *ValidatorManager {
 	return &ValidatorManager{
 		quorumSize:            big.NewInt(0),
 		backend:               backend,