diff --git a/acme/client.go b/acme/client.go
index e55dd495..2ddb649b 100644
--- a/acme/client.go
+++ b/acme/client.go
@@ -11,7 +11,9 @@ import (
 	"net/http"
 	"os"
 	"regexp"
+	"strconv"
 	"strings"
+	"time"
 )
 
 // Logger is used to log errors; if nil, the default log.Logger is used.
@@ -163,6 +165,7 @@ func (c *Client) ObtainCertificates(domains []string) ([]CertificateResource, er
 	return c.requestCertificates(challenges)
 }
 
+// RevokeCertificate takes a DER encoded certificate and tries to revoke it at the CA.
 func (c *Client) RevokeCertificate(certificate []byte) error {
 	encodedCert := base64.URLEncoding.EncodeToString(certificate)
 
@@ -287,44 +290,102 @@ func (c *Client) getChallenges(domains []string) []*authorizationResource {
 // It then uses these to request a certificate from the CA and returns the list of successfully
 // granted certificates.
 func (c *Client) requestCertificates(challenges []*authorizationResource) ([]CertificateResource, error) {
-	var certs []CertificateResource
+	resc, errc := make(chan CertificateResource), make(chan error)
 	for _, authz := range challenges {
-		privKey, err := generatePrivateKey(c.keyBits)
-		if err != nil {
-			return nil, err
-		}
-
-		csr, err := generateCsr(privKey, authz.Domain)
-		if err != nil {
-			return nil, err
-		}
-		csrString := base64.URLEncoding.EncodeToString(csr)
-		jsonBytes, err := json.Marshal(csrMessage{Resource: "new-cert", Csr: csrString, Authorizations: []string{authz.AuthURL}})
-		if err != nil {
-			return nil, err
-		}
-
-		resp, err := c.jws.post(authz.NewCertURL, jsonBytes)
-		if err != nil {
-			return nil, err
-		}
-
-		if resp.Header.Get("Content-Type") != "application/pkix-cert" {
-			return nil, fmt.Errorf("The server returned an unexpected content-type header: %s - expected %s", resp.Header.Get("Content-Type"), "application/pkix-cert")
-		}
-
-		cert, err := ioutil.ReadAll(resp.Body)
-		if err != nil {
-			return nil, err
-		}
-
-		privateKeyPem := pemEncode(privKey)
-
-		certs = append(certs, CertificateResource{Domain: authz.Domain, CertURL: resp.Header.Get("Location"), PrivateKey: privateKeyPem, Certificate: cert})
+		go c.requestCertificate(authz, resc, errc)
 	}
+
+	var certs []CertificateResource
+	for i := 0; i < len(challenges); i++ {
+		select {
+		case res := <-resc:
+			certs = append(certs, res)
+		case err := <-errc:
+			logger().Printf("%v", err)
+		}
+	}
+
 	return certs, nil
 }
 
+func (c *Client) requestCertificate(authz *authorizationResource, result chan CertificateResource, errc chan error) {
+	privKey, err := generatePrivateKey(c.keyBits)
+	if err != nil {
+		errc <- err
+		return
+	}
+
+	csr, err := generateCsr(privKey, authz.Domain)
+	if err != nil {
+		errc <- err
+		return
+	}
+
+	csrString := base64.URLEncoding.EncodeToString(csr)
+	jsonBytes, err := json.Marshal(csrMessage{Resource: "new-cert", Csr: csrString, Authorizations: []string{authz.AuthURL}})
+	if err != nil {
+		errc <- err
+		return
+	}
+
+	resp, err := c.jws.post(authz.NewCertURL, jsonBytes)
+	if err != nil {
+		errc <- err
+		return
+	}
+
+	privateKeyPem := pemEncode(privKey)
+	cerRes := CertificateResource{
+		Domain:     authz.Domain,
+		CertURL:    resp.Header.Get("Location"),
+		PrivateKey: privateKeyPem}
+
+	for {
+
+		switch resp.StatusCode {
+		case 202:
+		case 201:
+
+			cert, err := ioutil.ReadAll(resp.Body)
+			if err != nil {
+				errc <- err
+				return
+			}
+
+			// The server returns a body with a length of zero if the
+			// certificate was not ready at the time this request completed.
+			// Otherwise the body is the certificate.
+			if len(cert) > 0 {
+				cerRes.CertStableURL = resp.Header.Get("Content-Location")
+				cerRes.Certificate = cert
+				result <- cerRes
+			} else {
+				// The certificate was granted but is not yet issued.
+				// Check retry-after and loop.
+				ra := resp.Header.Get("Retry-After")
+				retryAfter, err := strconv.Atoi(ra)
+				if err != nil {
+					errc <- err
+					return
+				}
+
+				logger().Printf("[%s] Server responded with status 202. Respecting retry-after of: %d", authz.Domain, retryAfter)
+				time.Sleep(time.Duration(retryAfter) * time.Millisecond)
+			}
+			break
+		default:
+			logger().Fatalf("[%s] The server returned an unexpected status code %d.", authz.Domain, resp.StatusCode)
+			return
+		}
+
+		resp, err = http.Get(cerRes.CertURL)
+		if err != nil {
+			errc <- err
+			return
+		}
+	}
+}
+
 func logResponseHeaders(resp *http.Response) {
 	logger().Println(resp.Status)
 	for k, v := range resp.Header {
diff --git a/acme/messages.go b/acme/messages.go
index c5c345c7..c36fb6c5 100644
--- a/acme/messages.go
+++ b/acme/messages.go
@@ -66,7 +66,7 @@ type challenge struct {
 	Status   string `json:"status,omitempty"`
 	URI      string `json:"uri,omitempty"`
 	Token    string `json:"token,omitempty"`
-	Tls      bool   `json:"tls,omitempty"`
+	TLS      bool   `json:"tls,omitempty"`
 }
 
 type csrMessage struct {
@@ -84,8 +84,9 @@ type revokeCertMessage struct {
 // PrivateKey and Certificate are both already PEM encoded
 // and can be directly written to disk.
 type CertificateResource struct {
-	Domain      string
-	CertURL     string
-	PrivateKey  []byte
-	Certificate []byte
+	Domain        string
+	CertURL       string
+	CertStableURL string
+	PrivateKey    []byte
+	Certificate   []byte
 }
diff --git a/acme/simple_http_challenge.go b/acme/simple_http_challenge.go
index 9cb4ffdd..f270042a 100644
--- a/acme/simple_http_challenge.go
+++ b/acme/simple_http_challenge.go
@@ -147,17 +147,17 @@ func (s *simpleHTTPChallenge) startHTTPSServer(domain string, token string) (net
 		return nil, fmt.Errorf("Could not start HTTP listener! -> %v", err)
 	}
 
-	jsonBytes, err := json.Marshal(challenge{Type: "simpleHttp", Token: token, Tls: true})
+	jsonBytes, err := json.Marshal(challenge{Type: "simpleHttp", Token: token, TLS: true})
 	if err != nil {
-		return nil, errors.New("startHTTPSServer: Failed to marshal network message...")
+		return nil, errors.New("startHTTPSServer: Failed to marshal network message")
 	}
 	signed, err := s.jws.signContent(jsonBytes)
 	if err != nil {
-		return nil, errors.New("startHTTPSServer: Failed to sign message...")
+		return nil, errors.New("startHTTPSServer: Failed to sign message")
 	}
 	signedCompact := signed.FullSerialize()
 	if err != nil {
-		return nil, errors.New("startHTTPSServer: Failed to serialize message...")
+		return nil, errors.New("startHTTPSServer: Failed to serialize message")
 	}
 
 	// The handler validates the HOST header and request type.