diff --git a/.travis.yml b/.travis.yml
index c9ed246..8d76147 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,6 +13,7 @@ script:
   - make prepare
   - make all
   - make lint
+  - make critic
   - make test
 
 cache:
diff --git a/Makefile b/Makefile
index 2f4f1e5..04a7219 100644
--- a/Makefile
+++ b/Makefile
@@ -58,6 +58,10 @@ test: vendor version.go
 lint: version.go
 	@golangci-lint run
 
+.PHONY: critic
+critic: version.go
+	@gocritic check-project "$(ROOT_DIR)"
+
 .PHONY: clean
 clean:
 	@git clean -xfd && \
@@ -69,7 +73,7 @@ docker:
 	@docker build --pull -t "$(IMAGE_NAME)" "$(ROOT_DIR)"
 
 .PHONY: prepare
-prepare: install-dep install-lint
+prepare: install-dep install-lint install-critic
 
 .PHONY: install-dep
 install-dep:
@@ -79,3 +83,7 @@ install-dep:
 install-lint:
 	@curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh \
 		| bash -s -- -b $(GOPATH)/bin $(GOLANGCI_LINT_VERSION)
+
+.PHONY: install-critic
+install-critic:
+	@go get -u github.com/go-critic/go-critic/...
diff --git a/config/config.go b/config/config.go
index d595ee1..7c6c7f3 100644
--- a/config/config.go
+++ b/config/config.go
@@ -114,13 +114,10 @@ func getAddr(host fmt.Stringer, port uint16) string {
 // fetches data from external sources. Parameters passed to this
 // function, should come from command line arguments.
 func NewConfig(debug, verbose bool, // nolint: gocyclo
-	bindIP net.IP, bindPort uint16,
-	publicIPv4 net.IP, PublicIPv4Port uint16,
-	publicIPv6 net.IP, publicIPv6Port uint16,
-	statsIP net.IP, statsPort uint16,
-	secret, adtag string,
-	statsdIP string, statsdPort uint16, statsdNetwork string, statsdPrefix string,
-	statsdTagsFormat string, statsdTags map[string]string) (*Config, error) {
+	bindIP, publicIPv4, publicIPv6, statsIP net.IP,
+	bindPort, publicIPv4Port, publicIPv6Port, statsPort, statsdPort uint16,
+	secret, adtag, statsdIP, statsdNetwork, statsdPrefix, statsdTagsFormat string,
+	statsdTags map[string]string) (*Config, error) {
 	secureMode := false
 	if strings.HasPrefix(secret, "dd") && len(secret) == 34 {
 		secureMode = true
@@ -149,8 +146,8 @@ func NewConfig(debug, verbose bool, // nolint: gocyclo
 			return nil, errors.Errorf("IP %s is not IPv4", publicIPv4.String())
 		}
 	}
-	if PublicIPv4Port == 0 {
-		PublicIPv4Port = bindPort
+	if publicIPv4Port == 0 {
+		publicIPv4Port = bindPort
 	}
 
 	if publicIPv6 == nil {
@@ -175,7 +172,7 @@ func NewConfig(debug, verbose bool, // nolint: gocyclo
 		BindIP:         bindIP,
 		BindPort:       bindPort,
 		PublicIPv4:     publicIPv4,
-		PublicIPv4Port: PublicIPv4Port,
+		PublicIPv4Port: publicIPv4Port,
 		PublicIPv6:     publicIPv6,
 		PublicIPv6Port: publicIPv6Port,
 		StatsIP:        statsIP,
diff --git a/config/urls.go b/config/urls.go
index bfa1def..5f4e6d8 100644
--- a/config/urls.go
+++ b/config/urls.go
@@ -42,7 +42,7 @@ func makeTMeURL(values url.Values) string {
 }
 
 func makeQRCodeURL(data string) string {
-	QRURL := url.URL{
+	qr := url.URL{
 		Scheme: "https",
 		Host:   "api.qrserver.com",
 		Path:   "v1/create-qr-code",
@@ -52,7 +52,7 @@ func makeQRCodeURL(data string) string {
 	values.Set("qzone", "4")
 	values.Set("format", "svg")
 	values.Set("data", data)
-	QRURL.RawQuery = values.Encode()
+	qr.RawQuery = values.Encode()
 
-	return QRURL.String()
+	return qr.String()
 }
diff --git a/main.go b/main.go
index a3637ab..712d92c 100644
--- a/main.go
+++ b/main.go
@@ -129,24 +129,22 @@ func main() {
 	}
 
 	conf, err := config.NewConfig(*debug, *verbose,
-		*bindIP, *bindPort,
-		*publicIPv4, *publicIPv4Port,
-		*publicIPv6, *publicIPv6Port,
-		*statsIP, *statsPort,
-		*secret, *adtag,
-		*statsdIP, *statsdPort, *statsdNetwork, *statsdPrefix,
-		*statsdTagsFormat, *statsdTags,
+		*bindIP, *publicIPv4, *publicIPv6, *statsIP,
+		*bindPort, *publicIPv4Port, *publicIPv6Port, *statsPort, *statsdPort,
+		*secret, *adtag, *statsdIP, *statsdNetwork, *statsdPrefix, *statsdTagsFormat,
+		*statsdTags,
 	)
 	if err != nil {
 		usage(err.Error())
 	}
 
 	atom := zap.NewAtomicLevel()
-	if conf.Debug {
+	switch {
+	case conf.Debug:
 		atom.SetLevel(zapcore.DebugLevel)
-	} else if conf.Verbose {
+	case conf.Verbose:
 		atom.SetLevel(zapcore.InfoLevel)
-	} else {
+	default:
 		atom.SetLevel(zapcore.ErrorLevel)
 	}
 	encoderCfg := zap.NewProductionEncoderConfig()
diff --git a/mtproto/rpc/handshake_response.go b/mtproto/rpc/handshake_response.go
index a8c522c..f3d2faa 100644
--- a/mtproto/rpc/handshake_response.go
+++ b/mtproto/rpc/handshake_response.go
@@ -19,10 +19,10 @@ type HandshakeResponse struct {
 func (r *HandshakeResponse) Bytes() []byte {
 	buf := &bytes.Buffer{}
 
-	buf.Write(r.Type[:])
-	buf.Write(r.Flags[:])
-	buf.Write(r.SenderPID[:])
-	buf.Write(r.PeerPID[:])
+	buf.Write(r.Type)
+	buf.Write(r.Flags)
+	buf.Write(r.SenderPID)
+	buf.Write(r.PeerPID)
 
 	return buf.Bytes()
 }
diff --git a/wrappers/mtproto_cipher.go b/wrappers/mtproto_cipher.go
index 363ecd6..9e7900f 100644
--- a/wrappers/mtproto_cipher.go
+++ b/wrappers/mtproto_cipher.go
@@ -41,9 +41,9 @@ func NewMiddleProxyCipher(conn StreamReadWriteCloser,
 func deriveKeys(purpose cipherPurpose, req *rpc.NonceRequest, resp *rpc.NonceResponse,
 	client, remote *net.TCPAddr, secret []byte) ([]byte, []byte) {
 	message := bytes.Buffer{}
-	message.Write(resp.Nonce[:])
-	message.Write(req.Nonce[:])
-	message.Write(req.CryptoTS[:])
+	message.Write(resp.Nonce)
+	message.Write(req.Nonce)
+	message.Write(req.CryptoTS)
 
 	clientIPv4 := emptyIP[:]
 	serverIPv4 := emptyIP[:]
@@ -70,13 +70,13 @@ func deriveKeys(purpose cipherPurpose, req *rpc.NonceRequest, resp *rpc.NonceRes
 	binary.LittleEndian.PutUint16(port[:], uint16(remote.Port))
 	message.Write(port[:])
 	message.Write(secret)
-	message.Write(resp.Nonce[:])
+	message.Write(resp.Nonce)
 
 	if client.IP.To4() == nil {
 		message.Write(client.IP.To16())
 		message.Write(remote.IP.To16())
 	}
-	message.Write(req.Nonce[:])
+	message.Write(req.Nonce)
 
 	data := message.Bytes()
 	md5sum := md5.Sum(data[1:]) // nolint: gas