diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 5c20dca4..c59a627a 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -25,4 +25,5 @@ https://github.com/em0ney
 https://github.com/zqben402
 https://github.com/dlackty
 https://github.com/amcintosh
-
+https://github.com/valiton
+https://github.com/joshgarnett
diff --git a/aws-es-proxy.go b/aws-es-proxy.go
index 4b3e0ad4..e9729ee2 100644
--- a/aws-es-proxy.go
+++ b/aws-es-proxy.go
@@ -87,6 +87,7 @@ type proxy struct {
 	password        string
 	realm           string
 	remoteTerminate bool
+	assumeRole      string
 }
 
 func newProxy(args ...interface{}) *proxy {
@@ -112,6 +113,7 @@ func newProxy(args ...interface{}) *proxy {
 		password:        args[8].(string),
 		realm:           args[9].(string),
 		remoteTerminate: args[10].(bool),
+		assumeRole:      args[11].(string),
 	}
 }
 
@@ -187,7 +189,6 @@ func (p *proxy) parseEndpoint() error {
 func (p *proxy) getSigner() *v4.Signer {
 	// Refresh credentials after expiration. Required for STS
 	if p.credentials == nil {
-
 		sess, err := session.NewSession(
 			&aws.Config{
 				Region:                        aws.String(p.region),
@@ -198,13 +199,26 @@ func (p *proxy) getSigner() *v4.Signer {
 			logrus.Debugln(err)
 		}
 
-		credentials := sess.Config.Credentials
 		awsRoleARN := os.Getenv("AWS_ROLE_ARN")
 		awsWebIdentityTokenFile := os.Getenv("AWS_WEB_IDENTITY_TOKEN_FILE")
+
+		var creds *credentials.Credentials
 		if awsRoleARN != "" && awsWebIdentityTokenFile != "" {
-			credentials = stscreds.NewWebIdentityCredentials(sess, awsRoleARN, "", awsWebIdentityTokenFile)
+			logrus.Infof("Using web identity credentials with role %s", awsRoleARN)
+			creds = stscreds.NewWebIdentityCredentials(sess, awsRoleARN, "", awsWebIdentityTokenFile)
+		} else if p.assumeRole != "" {
+			logrus.Infof("Assuming credentials from %s", p.assumeRole)
+			creds = stscreds.NewCredentials(sess, p.assumeRole, func(provider *stscreds.AssumeRoleProvider) {
+				provider.Duration = 17 * time.Minute
+				provider.ExpiryWindow = 13 * time.Minute
+				provider.MaxJitterFrac = 0.1
+			})
+		} else {
+			logrus.Infoln("Using default credentials")
+			creds = sess.Config.Credentials
 		}
-		p.credentials = credentials
+
+		p.credentials = creds
 		logrus.Infoln("Generated fresh AWS Credentials object")
 	}
 
@@ -264,7 +278,13 @@ func (p *proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 		// Sign the request with AWSv4
 		payload := bytes.NewReader(replaceBody(req))
-		signer.Sign(req, payload, p.service, p.region, time.Now())
+		_, err := signer.Sign(req, payload, p.service, p.region, time.Now())
+		if err != nil {
+			p.credentials = nil
+			logrus.Errorln("Failed to sign", err)
+			http.Error(w, "Failed to sign", http.StatusForbidden)
+			return
+		}
 	}
 
 	resp, err := p.httpClient.Do(req)
@@ -443,6 +463,7 @@ func main() {
 		err             error
 		timeout         int
 		remoteTerminate bool
+		assumeRole      string
 	)
 
 	flag.StringVar(&endpoint, "endpoint", "", "Amazon ElasticSearch Endpoint (e.g: https://dummy-host.eu-west-1.es.amazonaws.com)")
@@ -459,6 +480,7 @@ func main() {
 	flag.StringVar(&password, "password", "", "HTTP Basic Auth Password")
 	flag.StringVar(&realm, "realm", "", "Authentication Required")
 	flag.BoolVar(&remoteTerminate, "remote-terminate", false, "Allow HTTP remote termination")
+	flag.StringVar(&assumeRole, "assume", "", "Optionally specify role to assume")
 	flag.Parse()
 
 	if endpoint == "" {
@@ -505,6 +527,7 @@ func main() {
 		password,
 		realm,
 		remoteTerminate,
+		assumeRole,
 	)
 
 	if err = p.parseEndpoint(); err != nil {