diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java b/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java
index 5920e8fa..a0fbd4ff 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/Registration.java
@@ -14,6 +14,7 @@
 package org.shredzone.acme4j;
 
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -24,7 +25,7 @@ import java.util.List;
  */
 public class Registration {
 
-    private List<String> contacts = new ArrayList<>();
+    private List<URI> contacts = new ArrayList<>();
     private URI agreement;
     private URI location;
 
@@ -57,12 +58,40 @@ public class Registration {
     }
 
     /**
-     * List of contact email addresses.
+     * List of contact addresses (emails, phone numbers etc).
      */
-    public List<String> getContacts() {
+    public List<URI> getContacts() {
         return contacts;
     }
 
+    /**
+     * Add a contact URI to the list of contacts.
+     *
+     * @param contact
+     *            Contact URI
+     */
+    public void addContact(URI contact) {
+        getContacts().add(contact);
+    }
+
+    /**
+     * Add a contact address to the list of contacts.
+     * <p>
+     * This is a convenience call for {@link #addContact(URI)}.
+     *
+     * @param contact
+     *            Contact URI as string
+     * @throws IllegalArgumentException
+     *             if there is a syntax error in the URI string
+     */
+    public void addContact(String contact) {
+        try {
+            addContact(new URI(contact));
+        } catch (URISyntaxException ex) {
+            throw new IllegalArgumentException("Invalid contact URI", ex);
+        }
+    }
+
     /**
      * Location URI of the registration at the server. Returned from the server after
      * successfully creating or updating a registration.
diff --git a/acme4j-client/src/test/java/org/shredzone/acme4j/RegistrationTest.java b/acme4j-client/src/test/java/org/shredzone/acme4j/RegistrationTest.java
index 8102f4f8..4910b8bb 100644
--- a/acme4j-client/src/test/java/org/shredzone/acme4j/RegistrationTest.java
+++ b/acme4j-client/src/test/java/org/shredzone/acme4j/RegistrationTest.java
@@ -41,12 +41,15 @@ public class RegistrationTest {
 
         registration.setAgreement(new URI("http://example.com/agreement.pdf"));
         registration.setLocation(new URI("http://example.com/acme/12345"));
-        registration.getContacts().add("mailto:foo@example.com");
-        registration.getContacts().add("mailto:bar@example.com");
+        registration.getContacts().add(new URI("mailto:foo@example.com"));
+        registration.addContact(new URI("tel:+1-212-555-0101"));
+        registration.addContact("mailto:foo2@example.com");
 
         assertThat(registration.getAgreement(), is(new URI("http://example.com/agreement.pdf")));
         assertThat(registration.getLocation(), is(new URI("http://example.com/acme/12345")));
-        assertThat(registration.getContacts(), contains("mailto:foo@example.com", "mailto:bar@example.com"));
+        assertThat(registration.getContacts(), contains(
+                        new URI("mailto:foo@example.com"), new URI("tel:+1-212-555-0101"),
+                        new URI("mailto:foo2@example.com")));
     }
 
     /**
diff --git a/acme4j-client/src/test/java/org/shredzone/acme4j/impl/AbstractAcmeClientTest.java b/acme4j-client/src/test/java/org/shredzone/acme4j/impl/AbstractAcmeClientTest.java
index ae53f0a3..795b7eba 100644
--- a/acme4j-client/src/test/java/org/shredzone/acme4j/impl/AbstractAcmeClientTest.java
+++ b/acme4j-client/src/test/java/org/shredzone/acme4j/impl/AbstractAcmeClientTest.java
@@ -69,7 +69,7 @@ public class AbstractAcmeClientTest {
     @Test
     public void testNewRegistration() throws AcmeException {
         Registration registration = new Registration();
-        registration.getContacts().add("mailto:foo@example.com");
+        registration.addContact("mailto:foo@example.com");
 
         Connection connection = new DummyConnection() {
             @Override
@@ -111,7 +111,7 @@ public class AbstractAcmeClientTest {
     public void testUpdateRegistration() throws AcmeException {
         Registration registration = new Registration();
         registration.setAgreement(agreementUri);
-        registration.getContacts().add("mailto:foo2@example.com");
+        registration.addContact("mailto:foo2@example.com");
         registration.setLocation(locationUri);
 
         Connection connection = new DummyConnection() {
diff --git a/src/site/markdown/usage/register.md b/src/site/markdown/usage/register.md
index c734fc10..6c4074c5 100644
--- a/src/site/markdown/usage/register.md
+++ b/src/site/markdown/usage/register.md
@@ -8,7 +8,7 @@ This code fragment registers your account with the CA. Optionally you can add co
 
 ```java
 Registration reg = new Registration();
-reg.getContacts().add("mailto:acme@example.com"); // optional
+reg.addContact("mailto:acme@example.com"); // optional
 
 client.newRegistration(account, reg);